BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates to fluidic dispensing devices.
2. Description of the Related Art
[0002] One type of microfluidic dispensing device, such as an ink jet printhead, is designed
to include a capillary member, such as foam or felt, to control backpressure. In this
type of printhead, the only free fluid is present between a filter and the ejection
device. If settling or separation of the fluid occurs, it is almost impossible to
re-mix the fluid contained in the capillary member.
[0003] Another type of printhead is referred to in the art as a free fluid style printhead,
which has a movable wall that is spring loaded to maintain backpressure at the nozzles
of the printhead. One type of spring loaded movable wall uses a deformable deflection
bladder to create the spring and wall in a single piece. An early printhead design
by Hewlett-Packard Company used a circular deformable rubber part in the form of a
thimble shaped bladder positioned between a lid and a body that contained ink. The
deflection of the thimble shaped bladder collapsed on itself. The thimble shaped bladder
maintained backpressure by deforming the bladder material as ink was delivered to
the printhead chip.
[0004] In a fluid tank where separation of fluids and particulate may occur, it is desirable
to provide a mixing of the fluid. For example, particulate in pigmented fluids tend
to settle depending on particle size, specific gravity differences, and fluid viscosity.
U.S. Patent Application Publication No. 2006/0268080 discloses a system having an ink tank located remotely from the fluid ejection device,
wherein the ink tank contains a magnetic rotor, which is rotated by an external rotary
plate, to provide bulk mixing in the remote ink tank.
[0005] It has been recognized, however, that a microfluidic dispensing device having a compact
design, which includes both a fluid reservoir and an on-board fluid ejection chip,
presents particular challenges that a simple agitation in a remote tank does not address.
For example, it has been determined that not only does fluid in the bulk region of
the fluid reservoir need to be re-mixed, but remixing in the ejection chip region
also is desirable, and in some cases, may be necessary, in order to prevent the clogging
of the region near the fluid ejection chip with settled particulate.
[0006] Further, it has been recognized that even with remixing, there is a potential for
stagnation zones to be created in a fluid channel of a fluidic dispensing device,
wherein settled particulate is not affected by the fluid flow through the fluid channel
and/or a fluid flow through the fluid channel may result in an unintentional depositing
of particulate. Such stagnation zones may be created, for example, at locations in
the fluid channel where there are abrupt changes in the surface features, such as
in a corner defined by orthogonal planar surfaces.
[0007] What is needed in the art is a fluidic dispensing device having a moveable stir bar
that provides for both bulk fluid remixing and fluid remixing in the vicinity of the
fluid ejection chip, or a fluidic dispensing device having multiple stir bars that
provide for both bulk fluid remixing and fluid remixing in the vicinity of the fluid
ejection chip.
[0008] In addition, what is needed in the art is a method of operating a stir bar that includes
stir bar feedback, so as to facilitate efficient fluid re-mixing and redistribution
of particulate in the fluid within a fluid reservoir, or a fluidic dispensing device
having features to reduce stagnation zones in a fluid channel in the vicinity of the
ejection chip.
SUMMARY OF THE INVENTION
[0009] The present invention provides a fluidic dispensing device having a moveable stir
bar that facilitates both bulk fluid remixing and fluid remixing in the vicinity of
the fluid ejection chip. The present invention provides a fluidic dispensing device
having multiple stir bars that facilitate both bulk fluid remixing and fluid remixing
in the vicinity of the fluid ejection chip.
[0010] The present invention provides a method of operating a stir bar that includes stir
bar feedback, so as to facilitate efficient fluid re-mixing and redistribution of
particulate in the fluid within a fluid reservoir. The present invention provides
a fluidic dispensing device having features to reduce stagnation zones in a fluid
channel in the vicinity of the ejection chip.
[0011] The invention, in one form, is directed to a fluidic dispensing device that includes
a housing and a stir bar. The housing has an exterior wall and a fluid reservoir.
The exterior wall has a first opening in fluid communication with the fluid reservoir.
The stir bar is moveably confined within the fluid reservoir. The stir bar has a plurality
of paddles and a rotational axis, with each of the plurality of paddles that intermittently
faces toward the first opening.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The above-mentioned and other features and advantages of this invention, and the
manner of attaining them, will become more apparent and the invention will be better
understood by reference to the following description of embodiments of the invention
taken in conjunction with the accompanying drawings, wherein:
FIG. 1 is a perspective view of an embodiment of a microfluidic dispensing device
in accordance with the present invention, in an environment that includes an external
magnetic field generator.
FIG. 2 is another perspective view of the microfluidic dispensing device of FIG. 1.
FIG. 3 is a top orthogonal view of the microfluidic dispensing device of FIGs. 1 and
2.
FIG. 4 is a side orthogonal view of the microfluidic dispensing device of FIGs. 1
and 2.
FIG. 5 is an end orthogonal view of the microfluidic dispensing device of FIGs. 1
and 2.
FIG. 6 is an exploded perspective view of the microfluidic dispensing device of FIGs.
1 and 2, oriented for viewing into the chamber of the body in a direction toward the
ejection chip.
FIG. 7 is another exploded perspective view of the microfluidic dispensing device
of FIGs. 1 and 2, oriented for viewing in a direction away from the ejection chip.
FIG. 8 is a section view of the microfluidic dispensing device of FIG. 1, taken along
line 8-8 of FIG. 5.
FIG. 9 is a section view of the microfluidic dispensing device of FIG. 1, taken along
line 9-9 of FIG. 5.
FIG. 10 is a perspective view of the microfluidic dispensing device of FIG. 1, with
the end cap and lid removed to expose the body/diaphragm assembly.
FIG. 11 is a perspective view of the depiction of FIG. 10, with the diaphragm removed
to expose the guide portion and stir bar contained in the body, in relation to first
and second planes and to the fluid ejection direction.
FIG. 12 is an orthogonal view of the body/guide portion/stir bar arrangement of FIG.
11, as viewed in a direction into the body of the chamber toward the base wall of
the body.
FIG. 13 is an orthogonal end view of the body of FIG. 11, which contains the guide
portion and stir bar, as viewed in a direction toward the exterior wall and fluid
opening of the body.
FIG. 14 is a section view of the body/guide portion/stir bar arrangement of FIGs.
12 and 13, taken along line 14-14 of FIG. 13.
FIG. 15 is an enlarged section view of the body/guide portion/stir bar arrangement
of FIGs. 12 and 13, taken along line 15-15 of FIG. 13.
FIG. 16 is an enlarged view of the depiction of FIG. 12, with the guide portion removed
to expose the stir bar residing in the chamber of the body.
FIG. 17 is a top view of another embodiment of a microfluidic dispensing device in
accordance with the present invention.
FIG. 18 is a section view of the microfluidic dispensing device of FIG. 17, taken
along line 18-18 of FIG. 17.
FIG. 19 is an exploded perspective view of the microfluidic dispensing device of FIG.
17, oriented for viewing into the chamber of the body in a direction toward the ejection
chip.
FIG. 20 is another perspective view of the microfluidic dispensing device of FIG.
17, with the end cap, lid and diaphragm removed to expose the guide portion and stir
bar contained in the body, shown in relation to first and second planes and the fluid
ejection direction.
FIG. 21 is an orthogonal top view corresponding to the perspective view of FIG. 20,
showing the body having a chamber that contains the guide portion and the stir bar.
FIG. 22 is a side orthogonal view of the body of the microfluidic dispensing device
of FIG. 17, wherein the body contains the guide portion and the stir bar.
FIG. 23 is a section view taken along line 23-23 of FIG. 22.
FIG. 24 is a perspective view of an embodiment of the stir bar of the microfluidic
dispensing device of FIG. 17, as further depicted in FIGs. 18-21 and 23.
FIG. 25 is a top view of the stir bar of FIG. 24.
FIG. 26 is a side view of the stir bar of FIG. 24.
FIG. 27 is a section view of the stir bar taken along line 27-27 of FIG. 25.
FIG. 28 is a perspective view of another embodiment of a stir bar suitable for use
in the microfluidic dispensing device of FIG. 17.
FIG. 29 is a top view of the stir bar of FIG. 28.
FIG. 30 is a side view of the stir bar of FIG. 28.
FIG. 31 is a section view of the stir bar taken along line 31-31 of FIG. 29.
FIG. 32 is an exploded perspective view of another embodiment of a stir bar suitable
for use in the microfluidic dispensing device of FIG. 17.
FIG. 33 is a top view of the stir bar of FIG. 32.
FIG. 34 is a side view of the stir bar of FIG. 32.
FIG. 35 is a section view of the stir bar taken along line 35-35 of FIG. 33.
FIG. 36 is an exploded perspective view of another embodiment of a stir bar suitable
for use in the microfluidic dispensing device of FIG. 17.
FIG. 37 is a top view of the stir bar of FIG. 36.
FIG. 38 is a side view of the stir bar of FIG. 36.
FIG. 39 is a section view of the stir bar taken along line 39-39 of FIG. 37.
FIG. 40 is an exploded perspective view of another embodiment of a stir bar suitable
for use in the microfluidic dispensing device of FIG. 17.
FIG. 41 is a top view of the stir bar of FIG. 40.
FIG. 42 is a side view of the stir bar of FIG. 40.
FIG. 43 is a section view of the stir bar taken along line 43-43 of FIG. 41.
FIG. 44 is a top view of another embodiment of a stir bar suitable for use in the
microfluidic dispensing device of FIG. 17.
FIG. 45 is a side view of the stir bar of FIG. 45.
FIG. 46 is a section view of the stir bar taken along line 46-46 of FIG. 44.
FIG. 47 is an x-ray image of a microfluidic dispensing device configured in accordance
with FIGs. 17-23, which depicts an appropriate particulate suspension in the fluid,
such as a newly filled microfluidic dispensing device, or after implementation of
a method of the present invention to re-mix the fluid in the fluid reservoir.
FIG. 48 is an x-ray image of a microfluidic dispensing device configured in accordance
with FIGs. 17-23 having a longitudinal extent of the housing arranged along a vertical
axis, and showing an accumulation of settled particulate at a gravitational low region
of the fluid reservoir.
FIG. 49 is an x-ray image of the microfluidic dispensing device of FIG. 48, which
is tilted off-axis from the vertical axis to depict how settled particulate migrates
to a new gravitational low region of the fluid reservoir based on the change of orientation.
FIG. 50 is an x-ray image of a microfluidic dispensing device configured in accordance
with FIGs. 17-23, wherein the ejection chip faces vertically downward and settled
particulate has accumulated over the channel inlet and the channel outlet of the fluid
channel that feeds fluid to the ejection chip.
FIG. 51 is a perspective view of the microfluidic dispensing device of FIGs. 17-23,
shown in a Cartesian space having X, Y, and Z axes, with the longitudinal extent of
the housing on the positive Z-axis and the lateral extent of the housing lying on
the X-Y plane.
FIG. 52 shows the microfluidic dispensing device depicted in FIG. 18 at an orientation
wherein the fluid ejection direction is pointing upwardly at 135 degrees, and with
an exterior of the dome portion of the diaphragm facing upwardly and with an exterior
of the base wall facing downwardly.
FIG. 53 shows the microfluidic dispensing device depicted in FIG. 18 at an orientation
wherein the fluid ejection direction is at 45 degrees, and with the exterior of the
dome portion of the diaphragm facing downwardly at 45 degrees from vertical, and with
the exterior of the base wall facing upwardly at an angle of 45 degrees from vertical.
FIG. 54 is a block diagram of an external magnetic field generator used to rotate
the stir bar in the various embodiments of the present invention, and having a sensor.
FIG. 55 is a diagrammatic illustration of an angular rotational position of a stir
bar (with magnet) relative to the angular rotational position of a rotating magnetic
field.
FIG. 56 is a diagrammatic illustration and graphical depiction of a scenario wherein
the torque required to rotate a stir bar is too high to begin stir bar rotation, i.e.,
the stir bar is stuck and prevented from rotation.
FIG. 57 is a diagrammatic illustration and graphical depiction of a scenario wherein
there is a phase lag of approximately 45 degrees between the angular rotational position
of a stir bar and an angular rotational position of a rotating magnetic field.
FIG. 58 is a diagrammatic illustration and graphical depiction of a scenario wherein
there is a phase lag of approximately 90 degrees, represented by an arced arrowed
line, between the angular rotational position of a stir bar and an angular rotational
position of a rotating magnetic field.
FIG. 59 is a flowchart of a method of operating a stir bar in a fluidic dispensing
device, in accordance with an aspect of the present invention.
FIG. 60 is a further enlargement of a portion of the depiction of FIG. 23, illustrating
the locations of stagnation zones in the fluid channel.
FIG. 61 is a bottom view of an enlargement of a portion of the guide portion of FIG.
21, showing the flow control portion having an inlet flow director member and an outlet
flow director member.
FIG. 62 is an enlarged bottom perspective view of the guide portion of FIG. 21, at
an orientation that shows the flow control portion and the several surfaces of the
inlet flow director member.
FIG. 63 is an enlarged bottom perspective view of the guide portion of FIG. 21, at
an orientation that shows the flow control portion and the several surfaces of the
outlet flow director member.
FIG. 64 is a side orthogonal view of another embodiment of a microfluidic dispensing
device having features to reduce the occurrence of stagnation zones in the fluid channel.
FIG. 65 is a top orthogonal view of the microfluidic dispensing device of FIG. 51.
FIG. 66 is a section view of the microfluidic dispensing device taken along line 66-66
of FIG. 64.
FIG. 67 is a section view of the microfluidic dispensing device taken along line 67-67
of FIG. 64.
FIG. 68 is an enlargement of a portion of the depiction of FIG. 67.
FIG. 69 is a section view of the microfluidic dispensing device taken along line 69-69
of FIG. 65.
FIG. 70 is a section view of the microfluidic dispensing device taken along line 70-70
of FIG. 65.
FIG. 71 is an enlargement of a portion of the depiction of FIG. 70.
FIG. 72 is a perspective view of the microfluidic dispensing device of FIG. 1, with
the end cap and lid removed to expose the body/diaphragm assembly, in relation to
first and second planes and to the fluid ejection direction, and with a portion of
the diaphragm broken away to illustrate the fluid reservoir.
FIG. 73 is a top orthogonal view of the body/diaphragm assembly of FIG. 72.
FIG. 74 is a section view of the body/diaphragm assembly of FIG. 72, taken along line
74-74 of FIG. 73, to expose the multiple stir bars located in the fluid reservoir.
FIG. 75 is a perspective view of the depiction of FIG. 72, with the diaphragm removed
to expose the multiple stir bar contained in the body, and with the ejection chip
removed to expose the fluid opening in the exterior wall.
FIG. 76 is another perspective view of the depiction of FIG. 75, in an orientation
to show the channel inlet and channel outlet of a fluid channel.
FIG. 77 is a top orthogonal view of the body/stir bar components of FIGs. 75 and 76.
FIG. 78 is a diagrammatic depiction of the two stir bars depicted in FIGs. 73-77,
illustrating an overlap of a first rotational area of a first stir bar with a second
rotational area of a second stir bar.
FIG. 79 is a perspective view of an alternative body having a separation wall, which
may be substituted for the body depicted in FIGs. 1-5 and 72-77.
FIG. 80 is another perspective view of the depiction of FIG. 79, in an orientation
to show the channel inlet and channel outlet of a fluid channel in relation to the
separation wall.
FIG. 81 is a perspective view corresponding to the depiction of the alternative body
of FIGs. 79 and 80, with the two stir bars inserted on opposite sides of the separation
wall.
FIG. 82 is a top orthogonal view of the alternative body and stir bar components of
FIG. 81.
FIG. 83 is a section view of the alternative body of FIGs. 79-82, taken along line
83-83 of FIG. 82.
FIG. 84 is the section view of FIG. 83, modified to include a section view of the
diaphragm of FIGs. 72-74 installed on the alternative body of FIGs. 79-83.
FIG. 85 is an enlarged portion of the depiction of FIG. 82, illustrating the separation
wall separating a first rotational area of a first stir bar from a second rotational
area of a second stir bar.
FIG. 86 is a perspective view of the depiction of FIG. 72, with the diaphragm removed
to expose the stir bar contained in the body, and the ejection chip removed to expose
the fluid opening in the exterior wall.
FIG. 87 is another perspective view of the depiction of FIG. 72, in an orientation
to show the channel inlet and channel outlet of a fluid channel.
FIG. 88 is an orthogonal view of the body/stir bar arrangement of FIGs. 86 and 87,
as viewed in a direction into the body of the chamber toward the base wall of the
body.
FIG. 89 is a section view of the body/stir bar arrangement of FIG. 88, taken along
line 89-89 of FIG. 88.
FIG. 90 is a top view of another embodiment of a microfluidic dispensing device in
accordance with the present invention.
FIG. 91 is a section view of the microfluidic dispensing device of FIG. 90, taken
along line 91-91 of FIG. 90.
FIG. 92 is another perspective view of the microfluidic dispensing device of FIG.
90, with the end cap, lid and diaphragm removed to illustrate a range of motion of
the moveable stir bar with respect to the guide portion.
FIG. 93 is another perspective view of the microfluidic dispensing device of FIG.
90, with the end cap, lid and diaphragm removed to expose the guide portion and the
moveable stir bar contained in the body, shown in relation to first and second planes
and the fluid ejection direction.
FIG. 94 is an orthogonal top view corresponding to the perspective view of FIG. 93,
showing the body having a chamber that contains the guide portion and the moveable
stir bar, and illustrating the range of motion of the moveable stir bar with respect
to the guide portion.
FIG. 95 is a side orthogonal view of the body of the microfluidic dispensing device
of FIG. 90, wherein the body contains the guide portion and the moveable stir bar.
FIG. 96 is a section view taken along line 96-96 of FIG. 95.
FIG. 97 is a perspective view of an embodiment of the stir bar of the microfluidic
dispensing device of FIG. 90, as further depicted in FIGs. 91-94 and 96.
FIG. 98 is a top view of the stir bar of FIG. 97.
FIG. 99 is a side view of the stir bar of FIG. 97.
FIG. 100 is a section view of the stir bar of FIG. 97 taken along line 100-100 of
FIG. 98.
[0013] Corresponding reference characters indicate corresponding parts throughout the several
views. The exemplifications set out herein illustrate embodiments of the invention,
and such exemplifications are not to be construed as limiting the scope of the invention
in any manner.
DETAILED DESCRIPTION OF THE INVENTION
[0014] Referring now to the drawings, and more particularly to FIGs. 1-16, there is shown
a fluidic dispensing device, which in the present example is a microfluidic dispensing
device 110 in accordance with an embodiment of the present invention.
[0015] Referring to FIGs. 1-5, microfluidic dispensing device 110 generally includes a housing
112 and a tape automated bonding (TAB) circuit 114. Microfluidic dispensing device
110 is configured to contain a supply of a fluid, such as a fluid containing particulate
material, and TAB circuit 114 is configured to facilitate the ejection of the fluid
from housing 112. The fluid may be, for example, cosmetics, lubricants, paint, ink,
etc.
[0016] Referring also to FIGs. 6 and 7, TAB circuit 114 includes a flex circuit 116 to which
an ejection chip 118 is mechanically and electrically connected. Flex circuit 116
provides electrical connection to an electrical driver device (not shown), such as
an ink jet printer, configured to operate ejection chip 118 to eject the fluid that
is contained within housing 112. In the present embodiment, ejection chip 118 is configured
as a plate-like structure having a planar extent formed generally as a nozzle plate
layer and a silicon layer, as is well known in the art. The nozzle plate layer of
ejection chip 118 has a plurality of ejection nozzles 120 oriented such that a fluid
ejection direction 120-1 is substantially orthogonal to the planar extent of ejection
chip 118. Associated with each of the ejection nozzles 120, at the silicon layer of
ejection chip 118, is an ejection mechanism, such as an electrical heater (thermal)
or piezoelectric (electromechanical) device. The operation of such an ejection chip
118 and driver is well known in the micro-fluid ejection arts, such as in ink jet
printing.
[0017] As used herein, each of the terms substantially orthogonal and substantially perpendicular
is defined to mean an angular relationship between two elements of 90 degrees, plus
or minus 10 degrees. The term substantially parallel is defined to mean an angular
relationship between two elements of zero degrees, plus or minus 10 degrees.
[0018] As best shown in FIGs. 6 and 7, housing 112 includes a body 122, a lid 124, an end
cap 126, and a fill plug 128 (e.g., ball). Contained within housing 112 is a diaphragm
130, a stir bar 132, and a guide portion 134. Each of the housing 112 components,
stir bar 132, and guide portion 134 may be made of plastic, using a molding process.
Diaphragm 130 is made of rubber, using a molding process. Also, in the present embodiment,
fill plug 128 may be in the form of a stainless steel ball bearing.
[0019] Referring also to FIGs. 8 and 9, in general, a fluid (not shown) is loaded through
a fill hole 122-1 in body 122 (see also FIG. 6) into a sealed region, i.e., a fluid
reservoir 136, between body 122 and diaphragm 130. Back pressure in fluid reservoir
136 is set and then maintained by inserting, e.g., pressing, fill plug 128 into fill
hole 122-1 to prevent air from leaking into fluid reservoir 136 or fluid from leaking
out of fluid reservoir 136. End cap 126 is then placed onto an end of the body 122/lid
124 combination, opposite to ejection chip 118. Stir bar 132 resides in the sealed
fluid reservoir 136 between body 122 and diaphragm 130 that contains the fluid. An
internal fluid flow may be generated within fluid reservoir 136 by rotating stir bar
132 so as to provide fluid mixing and redistribution of particulate in the fluid within
the sealed region of fluid reservoir 136.
[0020] Referring now also to FIGs. 10-16, body 122 of housing 112 has a base wall 138 and
an exterior perimeter wall 140 contiguous with base wall 138. Exterior perimeter wall
140 is oriented to extend from base wall 138 in a direction that is substantially
orthogonal to base wall 138. Lid 124 is configured to engage exterior perimeter wall
140. Thus, exterior perimeter wall 140 is interposed between base wall 138 and lid
124, with lid 124 being attached to the open free end of exterior perimeter wall 140
by weld, adhesive, or other fastening mechanism, such as a snap fit or threaded union.
Attachment of lid 124 to body 122 occurs after installation of diaphragm 130, stir
bar 132, and guide portion 134 in body 122.
[0021] Exterior perimeter wall 140 of body 122 includes an exterior wall 140-1, which is
a contiguous portion of exterior perimeter wall 140. Exterior wall 140-1 has a chip
mounting surface 140-2 that defines a plane 142 (see FIGs. 11 and 12), and has a fluid
opening 140-3 adjacent to chip mounting surface 140-2 that passes through the thickness
of exterior wall 140-1. Ejection chip 118 is mounted, e.g., by an adhesive sealing
strip 144 (see FIGs. 6 and 7), to chip mounting surface 140-2 and is in fluid communication
with fluid opening 140-3 (see FIG. 13) of exterior wall 140-1. Thus, the planar extent
of ejection chip 118 is oriented along plane 142, with the plurality of ejection nozzles
120 oriented such that the fluid ejection direction 120-1 is substantially orthogonal
to plane 142. Base wall 138 is oriented along a plane 146 (see FIG. 11) that is substantially
orthogonal to plane 142 of exterior wall 140-1. As best shown in FIGs. 6, 15 and 16,
base wall 138 may include a circular recessed region 138-1 in the vicinity of the
desired location of stir bar 132.
[0022] Referring to FIGs. 11-16, body 122 of housing 112 also includes a chamber 148 located
within a boundary defined by exterior perimeter wall 140. Chamber 148 forms a portion
of fluid reservoir 136, and is configured to define an interior space, and in particular,
includes base wall 138 and has an interior perimetrical wall 150 configured to have
rounded corners, so as to promote fluid flow in chamber 148. Interior perimetrical
wall 150 of chamber 148 has an extent bounded by a proximal end 150-1 and a distal
end 150-2. Proximal end 150-1 is contiguous with, and may form a transition radius
with, base wall 138. Such an edge radius may help in mixing effectiveness by reducing
the number of sharp corners. Distal end 150-2 is configured to define a perimetrical
end surface 150-3 at a lateral opening 148-1 of chamber 148. Perimetrical end surface
150-3 may include a plurality of perimetrical ribs, or undulations, to provide an
effective sealing surface for engagement with diaphragm 130. The extent of interior
perimetrical wall 150 of chamber 148 is substantially orthogonal to base wall 138,
and is substantially parallel to the corresponding extent of exterior perimeter wall
140 (see FIG. 6).
[0023] As best shown in FIGs. 15 and 16, chamber 148 has an inlet fluid port 152 and an
outlet fluid port 154, each of which is formed in a portion of interior perimetrical
wall 150. The terms "inlet" and "outlet" are terms of convenience that are used in
distinguishing between the multiple ports of the present embodiment, and are correlated
with a particular rotational direction of stir bar 132. However, it is to be understood
that it is the rotational direction of stir bar 132 that dictates whether a particular
port functions as an inlet port or an outlet port, and it is within the scope of this
invention to reverse the rotational direction of stir bar 132, and thus reverse the
roles of the respective ports within chamber 148.
[0024] Inlet fluid port 152 is separated a distance from outlet fluid port 154 along a portion
of interior perimetrical wall 150. As best shown in FIGs. 15 and 16, considered together,
body 122 of housing 112 includes a fluid channel 156 interposed between the portion
of interior perimetrical wall 150 of chamber 148 and exterior wall 140-1 of exterior
perimeter wall 140 that carries ejection chip 118.
[0025] Fluid channel 156 is configured to minimize particulate settling in a region of ejection
chip 118. Fluid channel 156 is sized, e.g., using empirical data, to provide a desired
flow rate while also maintaining an acceptable fluid velocity for fluid mixing through
fluid channel 156.
[0026] In the present embodiment, referring to FIG. 15, fluid channel 156 is configured
as a U-shaped elongated passage having a channel inlet 156-1 and a channel outlet
156-2. Fluid channel 156 dimensions, e.g., height and width, and shape are selected
to provide a desired combination of fluid flow and fluid velocity for facilitating
intra-channel stirring.
[0027] Fluid channel 156 is configured to connect inlet fluid port 152 of chamber 148 in
fluid communication with outlet fluid port 154 of chamber 148, and also connects fluid
opening 140-3 of exterior wall 140-1 of exterior perimeter wall 140 in fluid communication
with both inlet fluid port 152 and outlet fluid port 154 of chamber 148. In particular,
channel inlet 156-1 of fluid channel 156 is located adjacent to inlet fluid port 152
of chamber 148 and channel outlet 156-2 of fluid channel 156 is located adjacent to
outlet fluid port 154 of chamber 148. In the present embodiment, the structure of
inlet fluid port 152 and outlet fluid port 154 of chamber 148 is symmetrical.
[0028] Fluid channel 156 has a convexly arcuate wall 156-3 that is positioned between channel
inlet 156-1 and channel outlet 156-2, with fluid channel 156 being symmetrical about
a channel mid-point 158. In turn, convexly arcuate wall 156-3 of fluid channel 156
is positioned between inlet fluid port 152 and outlet fluid port 154 of chamber 148
on the opposite side of interior perimetrical wall 150 from the interior space of
chamber 148, with convexly arcuate wall 156-3 positioned to face fluid opening 140-3
of exterior wall 140-1 and ejection chip 118.
[0029] Convexly arcuate wall 156-3 is configured to create a fluid flow through fluid channel
156 that is substantially parallel to ejection chip 118. In the present embodiment,
a longitudinal extent of convexly arcuate wall 156-3 has a radius that faces fluid
opening 140-3 and that is substantially parallel to ejection chip 118, and has transition
radii 156-4, 156-5 located adjacent to channel inlet 156-1 and channel outlet 156-2,
respectively. The radius and transition radii 156-4, 156-5 of convexly arcuate wall
156-3 help with fluid flow efficiency. A distance between convexly arcuate wall 156-3
and fluid ejection chip 118 is narrowest at the channel mid-point 158, which coincides
with a mid-point of the longitudinal extent of ejection chip 118, and in turn, with
a mid-point of the longitudinal extent of fluid opening 140-3 of exterior wall 140-1.
[0030] Each of inlet fluid port 152 and outlet fluid port 154 of chamber 148 has a beveled
ramp structure configured such that each of inlet fluid port 152 and outlet fluid
port 154 converges in a respective direction toward fluid channel 156. In particular,
inlet fluid port 152 of chamber 148 has a beveled inlet ramp 152-1 configured such
that inlet fluid port 152 converges, i.e., narrows, in a direction toward channel
inlet 156-1 of fluid channel 156, and outlet fluid port 154 of chamber 148 has a beveled
outlet ramp 154-1 that diverges, i.e., widens, in a direction away from channel outlet
156-2 of fluid channel 156.
[0031] Referring again to FIGs. 6-10, diaphragm 130 is positioned between lid 124 and perimetrical
end surface 150-3 of interior perimetrical wall 150 of chamber 148. The attachment
of lid 124 to body 122 compresses a perimeter of diaphragm 130 thereby creating a
continuous seal between diaphragm 130 and body 122. More particularly, diaphragm 130
is configured for sealing engagement with perimetrical end surface 150-3 of interior
perimetrical wall 150 of chamber 148 in forming fluid reservoir 136. Thus, in combination,
chamber 148 and diaphragm 130 cooperate to define fluid reservoir 136 having a variable
volume.
[0032] Referring particularly to FIGs. 6, 8 and 9, an exterior surface of diaphragm 130
is vented to the atmosphere through a vent hole 124-1 located in lid 124 so that a
controlled negative pressure can be maintained in fluid reservoir 136. Diaphragm 130
is made of rubber, and includes a dome portion 130-1 configured to progressively collapse
toward base wall 138 as fluid is depleted from microfluidic dispensing device 110,
so as to maintain a desired negative pressure in chamber 148, and thus changing the
effective volume of the variable volume of fluid reservoir 136.
[0033] Referring to FIGs. 8 and 9, for sake of further explanation, below, the variable
volume of fluid reservoir 136, also referred to herein as a bulk region, may be considered
to have a proximal continuous 1/3 volume portion 136-1, and a continuous 2/3 volume
portion 136-4 that is formed from a central continuous 1/3 volume portion 136-2 and
a distal continuous 1/3 volume portion 136-3, with the central continuous 1/3 volume
portion 136-2 separating the proximal continuous 1/3 volume portion 136-1 from the
distal continuous 1/3 volume portion 136-3. The proximal continuous 1/3 volume portion
136-1 is located closer to ejection chip 118 than the continuous 2/3 volume portion
136-4 that is formed from the central continuous 1/3 volume portion 136-2 and the
distal continuous 1/3 volume portion 136-3.
[0034] Referring to FIGs. 6-9 and 16, stir bar 132 resides in the variable volume of fluid
reservoir 136 and chamber 148, and is located within a boundary defined by the interior
perimetrical wall 150 of chamber 148. Stir bar 132 has a rotational axis 160 and a
plurality of paddles 132-1, 132-2, 132-3, 132-4 that radially extend away from the
rotational axis 160. Stir bar 132 has a magnet 162 (see FIG. 8), e.g., a permanent
magnet, configured for interaction with an external magnetic field generator 164 (see
FIG. 1) to drive stir bar 132 to rotate around the rotational axis 160. The principle
of stir bar 132 operation is that as magnet 162 is aligned to a strong enough external
magnetic field generated by external magnetic field generator 164, then rotating the
external magnetic field generated by external magnetic field generator 164 in a controlled
manner will rotate stir bar 132. The external magnetic field generated by external
magnetic field generator 164 may be rotated electronically, akin to the operation
of a stepper motor, or may be rotated via a rotating shaft. Thus, stir bar 132 is
effective to provide fluid mixing in fluid reservoir 136 by the rotation of stir bar
132 around the rotational axis 160.
[0035] Fluid mixing in the bulk region relies on a flow velocity caused by rotation of stir
bar 132 to create a shear stress at the settled boundary layer of the particulate.
When the shear stress is greater than the critical shear stress (empirically determined)
to start particle movement, remixing occurs because the settled particles are now
distributed in the moving fluid. The shear stress is dependent on both the fluid parameters
such as: viscosity, particle size, and density; and mechanical design factors such
as: container shape, stir bar 132 geometry, fluid thickness between moving and stationary
surfaces, and rotational speed.
[0036] Also, a fluid flow is generated by rotating stir bar 132 in a fluid region, e.g.,
the proximal continuous 1/3 volume portion 136-1 and fluid channel 156, associated
with ejection chip 118, so as to ensure that mixed bulk fluid is presented to ejection
chip 118 for nozzle ejection and to move fluid adjacent to ejection chip 118 to the
bulk region of fluid reservoir 136 to ensure that the channel fluid flowing through
fluid channel 156 mixes with the bulk fluid of fluid reservoir 136, so as to produce
a more uniform mixture. Although this flow is primarily distribution in nature, some
mixing will occur if the flow velocity is sufficient to create a shear stress above
the critical value.
[0037] Stir bar 132 primarily causes rotation flow of the fluid about a central region associated
with the rotational axis 160 of stir bar 132, with some axial flow with a central
return path as in a partial toroidal flow pattern.
[0038] Referring to FIG. 16, each paddle of the plurality of paddles 132-1, 132-2, 132-3,
132-4 of stir bar 132 has a respective free end tip 132-5. To reduce rotational drag,
each paddle may include upper and lower symmetrical pairs of chamfered surfaces, forming
leading beveled surfaces 132-6 and trailing beveled surfaces 132-7 relative to a rotational
direction 160-1 of stir bar 132. It is also contemplated that each of the plurality
of paddles 132-1, 132-2, 132-3, 132-4 of stir bar 132 may have a pill or cylindrical
shape. In the present embodiment, stir bar 132 has two pairs of diametrically opposed
paddles, wherein a first paddle of the diametrically opposed paddles has a first free
end tip 132-5 and a second paddle of the diametrically opposed paddles has a second
free end tip 132-5.
[0039] In the present embodiment, the four paddles forming the two pairs of diametrically
opposed paddles are equally spaced at 90 degree increments around the rotational axis
160. However, the actual number of paddles of stir bar 132 may be two or more, and
preferably three or four, but more preferably four, with each adjacent pair of paddles
having the same angular spacing around the rotational axis 160. For example, a stir
bar 132 configuration having three paddles may have a paddle spacing of 120 degrees,
having four paddles may have a paddle spacing of 90 degrees, etc.
[0040] In the present embodiment, and with the variable volume of fluid reservoir 136 being
divided as the proximal continuous 1/3 volume portion 136-1 and the continuous 2/3
volume portion 136-4 described above, with the proximal continuous 1/3 volume portion
136-1 being located closer to ejection chip 118 than the continuous 2/3 volume portion
136-4, the rotational axis 160 of stir bar 132 may be located in the proximal continuous
1/3 volume portion 136-1 that is closer to ejection chip 118. Stated differently,
guide portion 134 is configured to position the rotational axis 160 of stir bar 132
in a portion of the interior space of chamber 148 that constitutes a 1/3 of the volume
of the interior space of chamber 148 that is closest to fluid opening 140-3.
[0041] Referring again also to FIG. 11, the rotational axis 160 of stir bar 132 may be oriented
in an angular range of perpendicular, plus or minus 45 degrees, relative to the fluid
ejection direction 120-1. Stated differently, the rotational axis 160 of stir bar
132 may be oriented in an angular range of parallel, plus or minus 45 degrees, relative
to the planar extent (e.g., plane 142) of ejection chip 118. In combination, the rotational
axis 160 of stir bar 132 may be oriented in both an angular range of perpendicular,
plus or minus 45 degrees, relative the fluid ejection direction 120-1, and an angular
range of parallel, plus or minus 45 degrees, relative to the planar extent of ejection
chip 118.
[0042] More preferably, the rotational axis 160 has an orientation substantially perpendicular
to the fluid ejection direction 120-1, and thus, the rotational axis 160 of stir bar
132 has an orientation that is substantially parallel to plane 142, i.e., planar extent,
of ejection chip 118 and that is substantially perpendicular to plane 146 of base
wall 138. Also, in the present embodiment, the rotational axis 160 of stir bar 132
has an orientation that is substantially perpendicular to plane 146 of base wall 138
in all orientations around rotational axis 160 and is substantially perpendicular
to the fluid ejection direction 120-1.
[0043] Referring to FIGs. 6-9, 11, and 12, the orientations of stir bar 132, described above,
may be achieved by guide portion 134, with guide portion 134 also being located within
chamber 148 in the variable volume of fluid reservoir 136 (see FIGs. 8 and 9), and
more particularly, within the boundary defined by interior perimetrical wall 150 of
chamber 148. Guide portion 134 is configured to confine stir bar 132 in a predetermined
portion of the interior space of chamber 148 at a predefined orientation, as well
as to split and redirect the rotational fluid flow from stir bar 132 towards channel
inlet 156-1 of fluid channel 156. On the return flow side, guide portion 134 helps
to recombine the rotational flow received from channel outlet 156-2 of fluid channel
156 in the bulk region of fluid reservoir 136.
[0044] For example, guide portion 134 may be configured to position the rotational axis
160 of stir bar 132 in an angular range of parallel, plus or minus 45 degrees, relative
to the planar extent of ejection chip 118, and more preferably, guide portion 134
is configured to position the rotational axis 160 of stir bar 132 substantially parallel
to the planar extent of ejection chip 118. In the present embodiment, guide portion
134 is configured to position and maintain an orientation of the rotational axis 160
of stir bar 132 to be substantially parallel to the planar extent of ejection chip
118 and to be substantially perpendicular to plane 146 of base wall 138 in all orientations
around rotational axis 160.
[0045] Guide portion 134 includes an annular member 166, a plurality of locating features
168-1, 168-2, offset members 170, 172, and a cage structure 174. The plurality of
locating features 168-1, 168-2 are positioned on the opposite side of annular member
166 from offset members 170, 172, and are positioned to be engaged by diaphragm 130,
which keeps offset members 170, 172 in contact with base wall 138. Offset members
170, 172 maintain an axial position (relative to the rotational axis 160 of stir bar
132) of guide portion 134 in fluid reservoir 136. Offset member 172 includes a retention
feature 172-1 that engages body 122 to prevent a lateral translation of guide portion
134 in fluid reservoir 136.
[0046] Referring again to FIGs. 6 and 7, annular member 166 of guide portion 134 has a first
annular surface 166-1, a second annular surface 166-2, and an opening 166-3 that defines
an annular confining surface 166-4. Opening 166-3 of annular member 166 has a central
axis 176. Annular confining surface 166-4 is configured to limit radial movement of
stir bar 132 relative to the central axis 176. Second annular surface 166-2 is opposite
first annular surface 166-1, with first annular surface 166-1 being separated from
second annular surface 166-2 by annular confining surface 166-4. Referring also to
FIG. 9, first annular surface 166-1 of annular member 166 also serves as a continuous
ceiling over, and between, inlet fluid port 152 and outlet fluid port 154. The plurality
of offset members 170, 172 are coupled to annular member 166, and more particularly,
the plurality of offset members 170, 172 are connected to first annular surface 166-1
of annular member 166. The plurality of offset members 170, 172 are positioned to
extend from annular member 166 in a first axial direction relative to the central
axis 176. Each of the plurality of offset members 170, 172 has a free end configured
to engage base wall 138 of chamber 148 to establish an axial offset of annular member
166 from base wall 138. Offset member 172 also is positioned and configured to aid
in preventing a flow bypass of fluid channel 156.
[0047] The plurality of offset members 170, 172 are coupled to annular member 166, and more
particularly, the plurality of offset members 170, 172 are connected to second annular
surface 166-2 of annular member 166. The plurality of offset members 170, 172 are
positioned to extend from annular member 166 in a second axial direction relative
to the central axis 176, opposite to the first axial direction.
[0048] Thus, when assembled, each of locating features 168-1, 168-2 has a free end that
engages a perimetrical portion of diaphragm 130, and each of the plurality of offset
members 170, 172 have a free end that engages base wall 138.
[0049] Cage structure 174 of guide portion 134 is coupled to annular member 166 opposite
to the plurality of offset members 170, 172, and more particularly, the cage structure
174 has a plurality of offset legs 178 connected to second annular surface 166-2 of
annular member 166. Cage structure 174 has an axial restraint portion 180 that is
axially displaced by the plurality of offset legs 178 (three, as shown) from annular
member 166 in the second axial direction opposite to the first axial direction. As
shown in FIG. 12, axial restraint portion 180 is positioned over at least a portion
of the opening 166-3 in annular member 166 to limit axial movement of stir bar 132
relative to the central axis 176 in the second axial direction. Cage structure 174
also serves to prevent diaphragm 130 from contacting stir bar 132 as diaphragm displacement
(collapse) occurs during fluid depletion from fluid reservoir 136.
[0050] As such, in the present embodiment, stir bar 132 is confined within the region defined
by opening 166-3 and annular confining surface 166-4 of annular member 166, and between
axial restraint portion 180 of the cage structure 174 and base wall 138 of chamber
148. The extent to which stir bar 132 is movable within fluid reservoir 136 is determined
by the radial tolerances provided between annular confining surface 166-4 and stir
bar 132 in the radial direction, and by the axial tolerances between stir bar 132
and the axial limit provided by the combination of base wall 138 and axial restraint
portion 180. For example, the tighter the radial and axial tolerances provided by
guide portion 134, the less variation of the rotational axis 160 of stir bar 132 from
perpendicular relative to base wall 138, and the less side-to-side motion of stir
bar 132 within fluid reservoir 136.
[0051] In the present embodiment, guide portion 134 is configured as a unitary insert member
that is removably attached to housing 112. Guide portion 134 includes retention feature
172-1 and body 122 of housing 112 includes a second retention feature 182. First retention
feature 172-1 is engaged with second retention feature 182 to attach guide portion
134 to body 122 of housing 112 in a fixed relationship with housing 112. The first
retention feature 172-1/second retention feature 182 may be, for example, in the form
of a tab/slot arrangement, or alternatively, a slot/tab arrangement, respectively.
[0052] Referring to FIGs. 7 and 15, guide portion 134 may further include a flow control
portion 184, which in the present embodiment, also serves as offset member 172. Referring
to FIG. 15, flow control portion 184 has a flow separator feature 184-1, a flow rejoining
feature 184-2, and a concavely arcuate surface 184-3. Concavely arcuate surface 184-3
is coextensive with, and extends between, each of flow separator feature 184-1 and
flow rejoining feature 184-2. Each of flow separator feature 184-1 and flow rejoining
feature 184-2 is defined by a respective angled, i.e., beveled, wall. Flow separator
feature 184-1 is positioned adjacent inlet fluid port 152 and flow rejoining feature
184-2 is positioned adjacent outlet fluid port 154.
[0053] The beveled wall of flow separator feature 184-1 positioned adjacent to inlet fluid
port 152 of chamber 148 cooperates with beveled inlet ramp 152-1 of inlet fluid port
152 of chamber 148 to guide fluid toward channel inlet 156-1 of fluid channel 156.
Flow separator feature 184-1 is configured such that the rotational flow is directed
toward channel inlet 156-1 instead of allowing a direct bypass of fluid into the outlet
fluid that exits channel outlet 156-2. Referring also to FIGs. 9 and 14, positioned
opposite beveled inlet ramp 152-1 is the fluid ceiling provided by first annular surface
166-1 of annular member 166. Flow separator feature 184-1 in combination with the
continuous ceiling of annular member 166 and beveled ramp wall provided by beveled
inlet ramp 152-1 of inlet fluid port 152 of chamber 148 aids in directing a fluid
flow into channel inlet 156-1 of fluid channel 156.
[0054] Likewise, referring to FIGs. 9, 14 and 15, the beveled wall of flow rejoining feature
184-2 positioned adjacent to outlet fluid port 154 of chamber 148 cooperates with
beveled outlet ramp 154-1 of outlet fluid port 154 to guide fluid away from channel
outlet 156-2 of fluid channel 156. Positioned opposite beveled outlet ramp 154-1 is
the fluid ceiling provided by first annular surface 166-1 of annular member 166.
[0055] In the present embodiment, flow control portion 184 is a unitary structure formed
as offset member 172 of guide portion 134. Alternatively, all or a portion of flow
control portion 184 may be incorporated into interior perimetrical wall 150 of chamber
148 of body 122 of housing 112.
[0056] In the present embodiment, as best shown in FIGs. 15 and 16, stir bar 132 is oriented
such that the plurality of paddles 132-1, 132-2, 132-3, 132-4 periodically face the
concavely arcuate surface 184-3 of the flow control portion 184 as stir bar 132 is
rotated about the rotational axis 160. Stir bar 132 has a stir bar radius from rotational
axis 160 to the free end tip 132-5 of a respective paddle. A ratio of the stir bar
radius and a clearance distance between the free end tip 132-5 and flow control portion
184 may be 5:2 to 5:0.025. More particularly, guide portion 134 is configured to confine
stir bar 132 in a predetermined portion of the interior space of chamber 148. In the
present example, a distance between the respective free end tip 132-5 of each of the
plurality of paddles 132-1, 132-2, 132-3, 132-4 and concavely arcuate surface 184-3
of flow control portion 184 is in a range of 2.0 millimeters to 0.1 millimeters, and
more preferably, is in a range of 1.0 millimeters to 0.1 millimeters, as the respective
free end tip 132-5 faces concavely arcuate surface 184-3. Also, it has been found
that it is preferred to position stir bar 132 as close to ejection chip 118 as possible
so as to maximize flow through fluid channel 156.
[0057] Also, guide portion 134 is configured to position the rotational axis 160 of stir
bar 132 in a portion of fluid reservoir 136 such that the free end tip 132-5 of each
of the plurality of paddles 132-1, 132-2, 132-3, 132-4 of stir bar 132 rotationally
ingresses and egresses a proximal continuous 1/3 volume portion 136-1 that is closer
to ejection chip 118. Stated differently, guide portion 134 is configured to position
the rotational axis 160 of stir bar 132 in a portion of the interior space such that
the free end tip 132-5 of each of the plurality of paddles 132-1, 132-2, 132-3, 132-4
rotationally ingresses and egresses the continuous 1/3 volume portion 136-1 of the
interior space of chamber 148 that includes inlet fluid port 152 and outlet fluid
port 154.
[0058] More particularly, in the present embodiment, wherein stir bar 132 has four paddles,
guide portion 134 is configured to position the rotational axis 160 of stir bar 132
in a portion of the interior space such that the first and second free end tips 132-5
of each the two pairs of diametrically opposed paddles 132-1, 132-3 and 132-2, 132-4
alternatingly and respectively are positioned in the proximal continuous 1/3 volume
portion 136-1 of the volume of the interior space of chamber 148 that includes inlet
fluid port 152 and outlet fluid port 154 and in the continuous 2/3 volume portion
136-4 having the distal continuous 1/3 volume portion 136-3 of the interior space
that is furthest from ejection chip 118.
[0059] FIGs. 17-27 depict another embodiment of the invention, which in the present example
is in the form of a microfluidic dispensing device 210. Elements common to both microfluidic
dispensing device 110 and microfluidic dispensing device 210 are identified using
common element numbers, and for brevity, are not described again below in full detail.
[0060] Microfluidic dispensing device 210 generally includes a housing 212 and TAB circuit
114, with microfluidic dispensing device 210 configured to contain a supply of a fluid,
such as a particulate carrying fluid, and with TAB circuit 114 configured to facilitate
the ejection of the fluid from housing 212.
[0061] As best shown in FIGs. 17-19, housing 212 includes a body 214, a lid 216, an end
cap 218, and a fill plug 220 (e.g., ball). Contained within housing 212 is a diaphragm
222, a stir bar 224, and a guide portion 226. Each of housing 212 components, stir
bar 224, and guide portion 226 may be made of plastic, using a molding process. Diaphragm
222 is made of rubber, using a molding process. Also, in the present embodiment, fill
plug 220 may be in the form of a stainless steel ball bearing.
[0062] Referring to FIG. 18, in general, a fluid (not shown) is loaded through a fill hole
214-1 in body 214 (see FIG. 6) into a sealed region, i.e., a fluid reservoir 228,
between body 214 and diaphragm 222. Back pressure in fluid reservoir 228 is set and
then maintained by inserting, e.g., pressing, fill plug 220 into fill hole 214-1 to
prevent air from leaking into fluid reservoir 228 or fluid from leaking out of fluid
reservoir 228. End cap 218 is then placed onto an end of the body 214/lid 216 combination,
opposite to ejection chip 118. Stir bar 224 resides in the sealed fluid reservoir
228 between body 214 and diaphragm 222 that contains the fluid. An internal fluid
flow may be generated within fluid reservoir 228 by rotating stir bar 224 so as to
provide fluid mixing and redistribution of particulate within the sealed region of
fluid reservoir 228.
[0063] Referring now also to FIGs. 20 and 21, body 214 of housing 212 has a base wall 230
and an exterior perimeter wall 232 contiguous with base wall 230. Exterior perimeter
wall 232 is oriented to extend from base wall 230 in a direction that is substantially
orthogonal to base wall 230. Referring to FIG. 19, lid 216 is configured to engage
exterior perimeter wall 232. Thus, exterior perimeter wall 232 is interposed between
base wall 230 and lid 216, with lid 216 being attached to the open free end of exterior
perimeter wall 232 by weld, adhesive, or other fastening mechanism, such as a snap
fit or threaded union.
[0064] Referring also to FIGs. 18, 22 and 23, exterior perimeter wall 232 of body 214 includes
an exterior wall 232-1, which is a contiguous portion of exterior perimeter wall 232.
Exterior wall 232-1 has a chip mounting surface 232-2 and a fluid opening 232-3 adjacent
to chip mounting surface 232-2 that passes through the thickness of exterior wall
232-1.
[0065] Referring again also to FIG. 20, chip mounting surface 232-2 defines a plane 234.
Ejection chip 118 is mounted to chip mounting surface 232-2 and is in fluid communication
with fluid opening 232-3 of exterior wall 232-1. An adhesive sealing strip 144 holds
ejection chip 118 and TAB circuit 114 in place while a dispensed adhesive under ejection
chip 118, and the encapsulant to protect the electrical leads, is cured. After the
cure cycle, the liquid seal between ejection chip 118 and chip mounting surface 232-2
of body 214 is the die bond adhesive.
[0066] The planar extent of ejection chip 118 is oriented along the plane 234, with the
plurality of ejection nozzles 120 (see e.g., FIG. 1) oriented such that the fluid
ejection direction 120-1 is substantially orthogonal to the plane 234. Base wall 230
is oriented along a plane 236 that is substantially orthogonal to the plane 234 of
exterior wall 232-1, and is substantially parallel to the fluid ejection direction
120-1.
[0067] As best illustrated in FIG. 20, body 214 of housing 212 includes a chamber 238 located
within a boundary defined by exterior perimeter wall 232. Chamber 238 forms a portion
of fluid reservoir 228, and is configured to define an interior space, and in particular,
includes base wall 230 and has an interior perimetrical wall 240 configured to have
rounded corners, so as to promote fluid flow in chamber 238. Referring to FIG. 19,
interior perimetrical wall 240 of chamber 238 has an extent bounded by a proximal
end 240-1 and a distal end 240-2. Proximal end 240-1 is contiguous with, and preferably
forms a transition radius with, base wall 230. Distal end 240-2 is configured to define
a perimetrical end surface 240-3 at a lateral opening 238-1 of chamber 238. Perimetrical
end surface 240-3 may include a plurality of ribs, or undulations, to provide an effective
sealing surface for engagement with diaphragm 222. The extent of interior perimetrical
wall 240 of chamber 238 is substantially orthogonal to base wall 230, and is substantially
parallel to the corresponding extent of exterior perimeter wall 232.
[0068] As best shown in FIG. 19, chamber 238 has an inlet fluid port 242 and an outlet fluid
port 244, each of which is formed in a portion of interior perimetrical wall 240.
Inlet fluid port 242 is separated a distance from outlet fluid port 244 along the
portion of interior perimetrical wall 240. The terms "inlet" and "outlet" are terms
of convenience that are used in distinguishing between the multiple ports of the present
embodiment, and are correlated with a particular rotational direction 250-1 of stir
bar 224. However, it is to be understood that it is the rotational direction of stir
bar 224 that dictates whether a particular port functions as an inlet port or an outlet
port, and it is within the scope of this invention to reverse the rotational direction
of stir bar 224, and thus reverse the roles of the respective ports within chamber
238.
[0069] As best shown in FIG. 23, body 214 of housing 212 includes a fluid channel 246 interposed
between a portion of interior perimetrical wall 240 of chamber 238 and exterior wall
232-1 of exterior perimeter wall 232 that carries ejection chip 118. Fluid channel
246 is configured to minimize particulate settling in a region of fluid opening 232-3,
and in turn, ejection chip 118.
[0070] In the present embodiment, fluid channel 246 is configured as a U-shaped elongated
passage having a channel inlet 246-1 and a channel outlet 246-2. Fluid channel 246
dimensions, e.g., height and width, and shape are selected to provide a desired combination
of fluid flow and fluid velocity for facilitating intra-channel stirring.
[0071] Fluid channel 246 is configured to connect inlet fluid port 242 of chamber 238 in
fluid communication with outlet fluid port 244 of chamber 238, and also connects fluid
opening 232-3 of exterior wall 232-1 of exterior perimeter wall 232 in fluid communication
with both inlet fluid port 242 and outlet fluid port 244 of chamber 238. In particular,
channel inlet 246-1 of fluid channel 246 is located adjacent to inlet fluid port 242
of chamber 238 and channel outlet 246-2 of fluid channel 246 is located adjacent to
outlet fluid port 244 of chamber 238. In the present embodiment, the structure of
inlet fluid port 242 and outlet fluid port 244 of chamber 238 is symmetrical.
[0072] Fluid channel 246 has a convexly arcuate wall 246-3 that is positioned between channel
inlet 246-1 and channel outlet 246-2, with fluid channel 246 being symmetrical about
a channel mid-point 248. In turn, convexly arcuate wall 246-3 of fluid channel 246
is positioned between inlet fluid port 242 and outlet fluid port 244 of chamber 238
on the opposite side of interior perimetrical wall 240 from the interior space of
chamber 238, with convexly arcuate wall 246-3 positioned to face fluid opening 232-3
of exterior wall 232-1 and fluid ejection chip 118.
[0073] Convexly arcuate wall 246-3 is configured to create a fluid flow substantially parallel
to ejection chip 118. In the present embodiment, a longitudinal extent of convexly
arcuate wall 246-3 has a radius that faces fluid opening 232-3, is substantially parallel
to ejection chip 118, and has transition radii 246-4, 246-5 located adjacent to channel
inlet 246-1 and channel outlet 246-2 surfaces, respectively. The radius and radii
of convexly arcuate wall 246-3 help with fluid flow efficiency. A distance between
convexly arcuate wall 246-3 and fluid ejection chip 118 is narrowest at the channel
mid-point 248, which coincides with a mid-point of the longitudinal extent of fluid
ejection chip 118, and in turn, with at a mid-point of the longitudinal extent of
fluid opening 232-3 of exterior wall 232-1.
[0074] Referring again also to FIG. 19, each of inlet fluid port 242 and outlet fluid port
244 of chamber 238 has a beveled ramp structure configured such that each of inlet
fluid port 242 and outlet fluid port 244 converges in a respective direction toward
fluid channel 246. In particular, inlet fluid port 242 of chamber 238 has a beveled
inlet ramp 242-1 configured such that inlet fluid port 242 converges, i.e., narrows,
in a direction toward channel inlet 246-1 of fluid channel 246, and outlet fluid port
244 of chamber 238 has a beveled outlet ramp 244-1 that diverges, i.e., widens, in
a direction away from channel outlet 246-2 of fluid channel 246.
[0075] Referring again to FIG. 18, diaphragm 222 is positioned between lid 216 and perimetrical
end surface 240-3 of interior perimetrical wall 240 of chamber 238. The attachment
of lid 216 to body 214 compresses a perimeter of diaphragm 222 thereby creating a
continuous seal between diaphragm 222 and body 122, and more particularly, diaphragm
222 is configured for sealing engagement with perimetrical end surface 240-3 of interior
perimetrical wall 240 of chamber 238 in forming fluid reservoir 228. Thus, in combination,
chamber 148 and diaphragm 222 cooperate to define fluid reservoir 228 having a variable
volume.
[0076] Referring particularly to FIGs. 18 and 19, an exterior surface of diaphragm 222 is
vented to the atmosphere through a vent hole 216-1 located in lid 216 so that a controlled
negative pressure can be maintained in fluid reservoir 228. Diaphragm 222 is made
of rubber, and includes a dome portion 222-1 configured to progressively collapse
toward base wall 230 as fluid is depleted from microfluidic dispensing device 210,
so as to maintain a desired negative pressure in chamber 238, and thus changing the
effective volume of the variable volume of fluid reservoir 228.
[0077] Referring to FIG. 18, for sake of further explanation, below, the variable volume
of fluid reservoir 228, also referred to herein as a bulk region, may be considered
to have a proximal continuous 1/3 volume portion 228-1, a central continuous 1/3 volume
portion 228-2, and a distal continuous 1/3 volume portion 228-3, with the central
continuous 1/3 volume portion 228-2 separating the proximal continuous 1/3 volume
portion 228-1 from the distal continuous 1/3 volume portion 228-3. The proximal continuous
1/3 volume portion 228-1 is located closer to ejection chip 118 than either of the
central continuous 1/3 volume portion 228-2 and the distal continuous 1/3 volume portion
228-3.
[0078] Referring to FIGs. 18 and 19, stir bar 224 resides in the variable volume of fluid
reservoir 228 and in chamber 238, and is located within a boundary defined by interior
perimetrical wall 240 of chamber 238. Referring also to FIGs. 24-27, stir bar 224
has a rotational axis 250 and a plurality of paddles 252, 254, 256, 258 that radially
extend away from the rotational axis 250. Stir bar 224 has a magnet 260 (see FIGs.
18, 23, and 27), e.g., a permanent magnet, configured for interaction with external
magnetic field generator 164 (see FIG. 1) to drive stir bar 224 to rotate around the
rotational axis 250. In the present embodiment, stir bar 224 has two pairs of diametrically
opposed paddles that are equally spaced at 90 degree increments around rotational
axis 250. However, the actual number of paddles of stir bar 224 is two or more, and
preferably three or four, but more preferably four, with each adjacent pair of paddles
having the same angular spacing around the rotational axis 250. For example, a stir
bar 224 configuration having three paddles would have a paddle spacing of 120 degrees,
having four paddles would have a paddle spacing of 90 degrees, etc.
[0079] In the present embodiment, as shown in FIGs. 24-27, stir bar 224 is configured in
a stepped, i.e., two-tiered, cross pattern with chamfered surfaces which may provide
the following desired attributes: quiet, short, low axial drag, good rotational speed
transfer, and capable of starting to mix with stir bar 224 in particulate sediment.
In particular, referring to FIG. 26, each of the plurality of paddles 252, 254, 256,
258 of stir bar 224 has an axial extent 262 having a first tier portion 264 and a
second tier portion 266. Referring also to FIG. 25, first tier portion 264 has a first
radial extent 268 terminating at a first distal end tip 270. Second tier portion 266
has a second radial extent 272 terminating in a second distal end tip 274. The first
radial extent 268 is greater than the second radial extent 272, such that a first
rotational velocity of first distal end tip 270 of first tier portion 264 is higher
than a second rotational velocity of second distal end tip 274 of second tier portion
266.
[0080] Also, in the present embodiment, the first radial extent 268 is not limited by a
cage containment structure, as in the previous embodiment, such that first distal
end tip 270 advantageously may be positioned closer to the surrounding portions of
interior perimetrical wall 240 of chamber 238, particularly in the central continuous
1/3 volume portion 228-2 and the distal continuous 1/3 volume portion 228-3. By reducing
the clearance between first distal end tip 270 and interior perimetrical wall 240
of chamber 238, mixing effectiveness is improved. Stir bar 224 has a stir bar radius
(first radial extent 268) from rotational axis 250 to the distal end tip 270 of first
tier portion 264 of a respective paddle. A ratio of the stir bar radius and a clearance
distance between the distal end tip 270 and its closest encounters with interior perimetrical
wall 240 may be 5:2 to 5:0.025. In the present example, such clearance at each of
the closest encounters may be in a range of 2.0 millimeters to 0.1 millimeters, and
more preferably, is in a range of 1.0 millimeters to 0.1 millimeters.
[0081] First tier portion 264 has a first tip portion 270-1 that includes first distal end
tip 270. First tip portion 270-1 may be tapered in a direction from the rotational
axis 250 toward first distal end tip 270. First tip portion of 270-1 of first tier
portion 264 has symmetrical upper and lower surfaces, each having a beveled, i.e.,
chamfered, leading surface and a beveled trailing surface. The beveled leading surfaces
and the beveled trailing surfaces of first tip portion 270-1 are configured to converge
at first distal end tip 270.
[0082] Also, in the present embodiment, first tier portion 264 of each of the plurality
of paddles 252, 254, 256, 258 collectively form a convex surface 276. As shown in
FIG. 18, convex surface 276 has a drag-reducing radius positioned to contact base
wall 230 of chamber 238. The drag-reducing radius may be, for example, at least three
times greater than the first radial extent 268 of first tier portion 264 of each of
the plurality of paddles 252, 254, 256, 258.
[0083] Referring again to FIG. 26, second tier portion 266 has a second tip portion 274-1
that includes second distal end tip 274. Second distal end tip 274 may have a radial
blunt end surface. Second tier portion 266 of each of the plurality of paddles 252,
254, 256, 258 has an upper surface having a beveled, i.e., chamfered, leading surface
and a beveled trailing surface.
[0084] Referring to FIGs. 19-27, the rotational axis 250 of stir bar 224 may be oriented
in an angular range of perpendicular, plus or minus 45 degrees, relative to the fluid
ejection direction 120-1. Stated differently, the rotational axis 250 of stir bar
224 may be oriented in an angular range of parallel, plus or minus 45 degrees, relative
to the planar extent (e.g., plane 234) of ejection chip 118. Also, rotational axis
250 of stir bar 224 may be oriented in an angular range of perpendicular, plus or
minus 45 degrees, relative to the planar extent of base wall 230. In combination,
the rotational axis 250 of stir bar 224 may be oriented in both an angular range of
perpendicular, plus or minus 45 degrees, relative the fluid ejection direction 120-1
and/or the planar extent of base wall 230, and an angular range of parallel, plus
or minus 45 degrees, relative to the planar extent of ejection chip 118.
[0085] More preferably, the rotational axis 250 has an orientation that is substantially
perpendicular to the fluid ejection direction 120-1, an orientation that is substantially
parallel to the plane 234, i.e., planar extent, of ejection chip 118, and an orientation
that is substantially perpendicular to the plane 236 of base wall 230. In the present
embodiment, the rotational axis 250 of stir bar 224 has an orientation that is substantially
perpendicular to the plane 236 of base wall 230 in all orientations around rotational
axis 250 and/or is substantially perpendicular to the fluid ejection direction 120-1
in all orientations around rotational axis 250.
[0086] The orientations of stir bar 224, described above, may be achieved by guide portion
226, with guide portion 226 also being located within chamber 238 in the variable
volume of fluid reservoir 228, and more particularly, within the boundary defined
by interior perimetrical wall 240 of chamber 238. Guide portion 226 is configured
to confine and position stir bar 224 in a predetermined portion of the interior space
of chamber 238 at one of the predefined orientations, described above.
[0087] Referring to FIGs, 18-21, for example, guide portion 226 may be configured to position
the rotational axis 250 of stir bar 224 in an angular range of parallel, plus or minus
45 degrees, relative to the planar extent of ejection chip 118, and more preferably,
guide portion 226 is configured to position the rotational axis 250 of stir bar 224
substantially parallel to the planar extent of ejection chip 118. In the present embodiment,
guide portion 226 is configured to position and maintain an orientation of the rotational
axis 250 of stir bar 224 to be substantially perpendicular to the plane 236 of base
wall 230 in all orientations around rotational axis 250 and to be substantially parallel
to the planar extent of ejection chip 118 in all orientations around rotational axis
250.
[0088] Referring to FIGs. 19-21 and 23, guide portion 226 includes an annular member 278,
and a plurality of mounting arms 280-1, 280-2, 280-3, 280-4 coupled to annular member
278. Annular member 278 has an opening 278-1 that defines an annular confining surface
278-2. Opening 278-1 has a central axis 282. Second tier portion 266 of stir bar 224
is received in opening 278-1 of annular member 278. Annular confining surface 278-2
is configured to contact the radial extent of second tier portion 266 of the plurality
of paddles 252, 254, 256, 258 to limit radial movement of stir bar 224 relative to
the central axis 282. Referring to FIGs. 18-20 and 23, annular member 278 has an axial
restraint surface 278-3 positioned to be axially offset from base wall 230 of chamber
238, for axial engagement with first tier portion 264 of stir bar 224.
[0089] Referring to FIGs. 20 and 21, the plurality of mounting arms 280-1, 280-2, 280-3,
280-4 are configured to engage housing 212 to suspend annular member 278 in the interior
space of chamber 238, separated from base wall 230 of chamber 238, with axial restraint
surface 278-3 positioned to face, and to be axially offset from, base wall 230 of
chamber 238. A distal end of each of mounting arms 280-1, 280-2, 280-3, 280-4 includes
respective locating features 280-5, 280-6, 280-7, 280-8 that have free ends to engage
a perimetrical portion of diaphragm 222.
[0090] In the present embodiment, base wall 230 limits axial movement of stir bar 224 relative
to the central axis 282 in a first axial direction and axial restraint surface 278-3
of annular member 278 is located to axially engage at least a portion of first tier
portion 264 of the plurality of paddles 252, 254, 256, 258 to limit axial movement
of stir bar 224 relative to the central axis 282 in a second axial direction opposite
to the first axial direction.
[0091] As such, in the present embodiment, stir bar 224 is confined within the region defined
by opening 278-1 and annular confining surface 278-2 of annular member 278, and between
axial restraint surface 278-3 of annular member 278 and base wall 230 of chamber 238.
The extent to which stir bar 224 is movable within fluid reservoir 228 is determined
by the radial tolerances provided between annular confining surface 278-2 and stir
bar 224 in the radial direction, and by the axial tolerances between stir bar 224
and the axial limit provided by the combination of base wall 230 and axial restraint
surface 278-3 of annular member 278. For example, the tighter the radial and axial
tolerances provided by guide portion 226, the less variation of the rotational axis
250 of stir bar 224 from perpendicular relative to base wall 230, and the less side-to-side
motion of stir bar 224 within fluid reservoir 228.
[0092] In the present embodiment, guide portion 226 is configured as a unitary insert member
that is removably attached to housing 212. Referring to FIG. 23, guide portion 226
includes a first retention feature 284 and body 214 of housing 212 includes a second
retention feature 214-2. First retention feature 284 is engaged with second retention
feature 214-2 to attach guide portion 226 to body 214 of housing 212 in a fixed relationship
with housing 212. First retention feature 284/second retention feature 214-2 combination
may be, for example, in the form of a tab/slot arrangement, or alternatively, a slot/tab
arrangement, respectively.
[0093] As best shown in FIG. 23 with respect to FIG. 19, guide portion 226 may further include
a flow control portion 286 having a flow separator feature 286-1, a flow rejoining
feature 286-2, and a concavely arcuate surface 286-3. Flow control portion 286 provides
an axial spacing between axial restraint surface 278-3 and base wall 230 in the region
of inlet fluid port 242 and outlet fluid port 244. Concavely arcuate surface 286-3
is coextensive with, and extends between, each of flow separator feature 286-1 and
flow rejoining feature 286-2. Flow separator feature 286-1 is positioned adjacent
inlet fluid port 242 and flow rejoining feature 286-2 is positioned adjacent outlet
fluid port 244. Flow separator feature 286-1 has a beveled wall that cooperates with
beveled inlet ramp 242-1 (see FIG. 19) of inlet fluid port 242 of chamber 238 to guide
fluid toward channel inlet 246-1 of fluid channel 246. Likewise, flow rejoining feature
286-2 has a beveled wall that cooperates with beveled outlet ramp 244-1 (see FIG.
19) of outlet fluid port 244 to guide fluid away from channel outlet 246-2 of fluid
channel 246.
[0094] It is contemplated that all, or a portion, of flow control portion 286 may be incorporated
into interior perimetrical wall 240 of chamber 238 of body 214 of housing 212.
[0095] In the present embodiment, as is best shown in FIG. 23, stir bar 224 is oriented
such that the free ends of the plurality of paddles 252, 254, 256, 258 periodically
face concavely arcuate surface 286-3 of flow control portion 286 as stir bar 224 is
rotated about the rotational axis 250. A ratio of the stir bar radius and a clearance
distance between the distal end tip 270 of first tier portion 264 of a respective
paddle and flow control portion 286 may be 5:2 to 5:0.025. More particularly, guide
portion 226 is configured to confine stir bar 224 in a predetermined portion of the
interior space of chamber 238. In the present example, a distance between first distal
end tip 270 and concavely arcuate surface 286-3 of flow control portion 286 is in
a range of 2.0 millimeters to 0.1 millimeters, and more preferably, is in a range
of 1.0 millimeters to 0.1 millimeters.
[0096] Also referring to FIG. 18, guide portion 226 is configured to position the rotational
axis 250 of stir bar 224 in a portion of fluid reservoir 228 such that first distal
end tip 270 of each of the plurality of paddles 252, 254, 256, 258 of stir bar 224
rotationally ingresses and egresses a proximal continuous 1/3 volume portion 228-1
of fluid reservoir 228 that is closer to ejection chip 118. Stated differently, guide
portion 226 is configured to position the rotational axis 250 of stir bar 224 in a
portion of the interior space such that first distal end tip 270 of each of the plurality
of paddles 252, 254, 256, 258 rotationally ingresses and egresses the continuous 1/3
volume portion 228-1 of the interior space of chamber 238 that includes inlet fluid
port 242 and outlet fluid port 244.
[0097] More particularly, in the present embodiment wherein stir bar 224 has four paddles,
guide portion 226 is configured to position the rotational axis 250 of stir bar 224
in a portion of the interior space of chamber 238 such that first distal end tip 270
of each the two pairs of diametrically opposed paddles alternatingly and respectively
are positioned in the proximal continuous 1/3 volume portion 228-1 of the volume of
the interior space of chamber 238 that includes inlet fluid port 242 and outlet fluid
port 244 and in the distal continuous 1/3 volume portion 228-3 of the interior space
that is furthest from ejection chip 118. More particularly, in the present embodiment
wherein stir bar 224 has two sets of diametrically opposed paddles, guide portion
226 is configured to position the rotational axis 250 of stir bar 224 in a portion
of the interior space of chamber 238 such that first distal end tip 270 of each of
diametrically opposed paddles, e.g., 252, 256 or 254, 258, as shown in FIG. 23, alternatingly
and respectively are positioned in the proximal continuous 1/3 volume portion 228-1
and the distal continuous 1/3 volume portion 228-3 as stir bar 224 is rotated.
[0098] FIGs. 28-31 show a configuration for a stir bar 300, which may be substituted for
stir bar 224 of microfluidic dispensing device 210 discussed above with respect to
the embodiment of FIGs. 17-27 for use with guide portion 226.
[0099] Stir bar 300 has a rotational axis 350 and a plurality of paddles 352, 354, 356,
358 that radially extend away from the rotational axis 350. Stir bar 300 has a magnet
360 (see FIG. 31), e.g., a permanent magnet, configured for interaction with external
magnetic field generator 164 (see FIG. 1) to drive stir bar 300 to rotate around the
rotational axis 350. In the present embodiment, stir bar 300 has two pairs of diametrically
opposed paddles that are equally spaced at 90 degree increments around rotational
axis 350.
[0100] In the present embodiment, as shown, stir bar 300 is configured in a stepped, i.e.,
two-tiered, cross pattern with chamfered surfaces. In particular, each of the plurality
of paddles 352, 354, 356, 358 of stir bar 300 has an axial extent 362 having a first
tier portion 364 and a second tier portion 366. First tier portion 364 has a first
radial extent 368 terminating at a first distal end tip 370. Second tier portion 366
has a second radial extent 372 terminating in a second distal end tip 374. The first
radial extent 368 is greater than the second radial extent 372, such that a first
rotational velocity of first distal end tip 370 of first tier portion 364 of stir
bar 300 is higher than a second rotational velocity of second distal end tip 374 of
second tier portion 366 of stir bar 300.
[0101] First tier portion 364 has a first tip portion 370-1 that includes first distal end
tip 370. First tip portion 370-1 may be tapered in a direction from the rotational
axis 350 toward first distal end tip 370. First tip portion 370-1 of first tier portion
364 has symmetrical upper and lower surfaces, each having a beveled, i.e., chamfered,
leading surface and a beveled trailing surface. The beveled leading surfaces and the
beveled trailing surfaces of first tip portion 370-1 are configured to converge at
first distal end tip 370. Also, in the present embodiment, first tier portion 364
of each of the plurality of paddles 352, 354, 356, 358 collectively form a flat surface
376 for engaging base wall 230.
[0102] Second tier portion 366 has a second tip portion 374-1 that includes second distal
end tip 374. Second distal end tip 374 may have a radially blunt end surface. Second
tier portion 366 has two diametrical pairs of upper surfaces, each having a beveled,
i.e., chamfered, leading surface and a beveled trailing surface. However, in the present
embodiment, the two diametrical pairs have different configurations, in that the area
of the upper beveled leading surface and upper beveled trailing surface for diametrical
pair of paddles 352, 356 is greater than the area of bevel of the upper beveled leading
surface and upper beveled trailing surface for diametrical pair of paddles 354, 358.
As such, adjacent angularly spaced pairs of the plurality of paddles 352, 354, 356,
358 alternatingly provide less and more aggressive agitation, respectively, of the
fluid in fluid reservoir 228.
[0103] FIGs. 32-35 show a configuration for a stir bar 400, which may be substituted for
stir bar 224 of microfluidic dispensing device 210 discussed above with respect to
the embodiment of FIGs. 17-27 for use with guide portion 226.
[0104] Stir bar 400 has a rotational axis 450 and a plurality of paddles 452, 454, 456,
458 that radially extend away from the rotational axis 450. Stir bar 400 has a magnet
460 (see FIGs. 32 and 35, e.g., a permanent magnet), configured for interaction with
external magnetic field generator 164 (see FIG. 1) to drive stir bar 400 to rotate
around the rotational axis 450. In the present embodiment, stir bar 400 has two pairs
of diametrically opposed paddles that are equally spaced at 90 degree increments around
rotational axis 450.
[0105] In the present embodiment, as shown, stir bar 400 is configured in a stepped, i.e.,
two-tiered, cross pattern. In particular, each of the plurality of paddles 452, 454,
456, 458 of stir bar 400 has an axial extent 462 having a first tier portion 464 and
a second tier portion 466. First tier portion 464 has a first radial extent 468 terminating
at a first distal end tip 470. Second tier portion 466 has a second radial extent
472 terminating in a second distal end tip 474 having a wide radial end shape. The
first radial extent 468 is greater than the second radial extent 472, such that a
first rotational velocity of first distal end tip 470 of first tier portion 464 of
stir bar 400 is higher than a second rotational velocity of second distal end tip
474 of second tier portion 466 of stir bar 400.
[0106] First tier portion 464 has a first tip portion 470-1 that includes first distal end
tip 370. First tip portion 470-1 may be tapered in a direction from the rotational
axis 450 toward first distal end tip 470. First tip portion 470-1 of first tier portion
464 has symmetrical upper and lower surfaces, each having a beveled, i.e., chamfered,
leading surface and a beveled trailing surface. The beveled leading surfaces and the
beveled trailing surfaces of first tip portion 470-1 are configured to converge at
first distal end tip 470. Also, in the present embodiment, first tier portion 464
of each of the plurality of paddles 452, 454, 456, 458 collectively form a flat surface
476 for engaging base wall 230.
[0107] Second tier portion 466 has a second tip portion 474-1 that includes second distal
end tip 474. Second tip portion 474-1 has a radially blunt end surface. Second tier
portion 466 has two diametrical pairs of upper surfaces. However, in the present embodiment,
the two diametrical pairs have different configurations, in that the diametrical pair
of paddles 452, 456 have upper beveled leading surfaces and upper beveled trailing
surfaces, and the diametrical pair of paddles 454, 458 do not, i.e., provide a blunt
lateral surface substantially parallel to rotational axis 450.
[0108] Referring again to FIGs. 32 and 35, stir bar 400 includes a void 478 that radially
intersects the rotational axis 450, with void 478 being located in the diametrical
pair of paddles 454, 458. Magnet 460 is positioned in void 478 with the north pole
of magnet 460 and the south pole of magnet 460 being diametrically opposed with respect
to the rotational axis 450. A film seal 480 is attached, e.g., by ultrasonic welding,
heat staking, laser welding, etc., to stir bar 400 to cover over void 478. It is preferred
that film seal 480 have a seal layer material that is chemically compatible with the
material of stir bar 400. Film seal 480 has a shape that conforms to the shape of
the upper surface of second tier portion 466 of diametrical pair of paddles 454, 458.
The present configuration has an advantage over a stir bar insert that is molded around
the magnet, since insert molding may slightly demagnetize the magnet from the insert
mold process heat.
[0109] FIGs. 36-39 show a configuration for a stir bar 400-1, having substantially the same
configuration as stir bar 400 discussed above with respect to FIGs. 32-35, with the
sole difference being the shape of the film seal used to seal void 478. Stir bar 400-1
has a film seal 480-1 having a circular shape, and which has a diameter that forms
an arcuate web between adjacent pairs of the plurality of paddles 452, 454, 456, 458.
The web features serve to separate the bulk mixing flow in the region between stir
bar 400-1 and diaphragm 222, and the regions between adjacent pairs of the plurality
of paddles 452, 454, 456, 458.
[0110] FIGs. 40-43 show a configuration for a stir bar 500, which may be substituted for
stir bar 224 of microfluidic dispensing device 210 discussed above with respect to
the embodiment of FIGs. 17-27 for use with guide portion 226.
[0111] Stir bar 500 has a cylindrical hub 502 having a rotational axis 550, and a plurality
of paddles 552, 554, 556, 558 that radially extend away from cylindrical hub 502.
Stir bar 500 has a magnet 560 (see FIGs. 40 and 43), e.g., a permanent magnet, configured
for interaction with external magnetic field generator 164 (see FIG. 1) to drive stir
bar 500 to rotate around the rotational axis 550.
[0112] In the present embodiment, as shown, the plurality of paddles 552, 554, 556, 558
of stir bar 500 are configured in a stepped, i.e., two-tiered, cross pattern with
chamfered surfaces. In particular, each of the plurality of paddles 552, 554, 556,
558 of stir bar 500 has an axial extent 562 having a first tier portion 564 and a
second tier portion 566. First tier portion 564 has a first radial extent 568 terminating
at a first distal end tip 570. Second tier portion 566 has a second radial extent
572 terminating in a second distal end tip 574.
[0113] First tier portion 564 has a first tip portion 570-1 that includes first distal end
tip 570. First tip portion 570-1 may be tapered in a direction from the rotational
axis 550 toward first distal end tip 570. First tip portion 570-1 of first tier portion
564 has symmetrical upper and lower surfaces, each having a beveled, i.e., chamfered,
leading surface and a beveled trailing surface. The beveled leading surfaces and the
beveled trailing surfaces of first tip portion 570-1 are configured to converge at
first distal end tip 570. First tier portion 564 of each of the plurality of paddles
552, 554, 556, 558, and cylindrical hub 502, collectively form a convexly curved surface
576 for engaging base wall 230.
[0114] The second tier portion 566 has a second tip portion 574-1 that includes second distal
end tip 574. Second distal end tip 574 may have a radially blunt end surface. Second
tier portion 566 has an upper surface having a chamfered leading surface and a chamfered
trailing surface.
[0115] Referring again to FIGs. 40 and 43, stir bar 500 includes a void 578 that radially
intersects the rotational axis 550, with void 578 being located in cylindrical hub
502. Magnet 560 is positioned in void 578 with the north pole of magnet 560 and the
south pole of magnet 560 being diametrically opposed with respect to the rotational
axis 550. A film seal 580 has a shape that conforms to the circular shape of the upper
surface of cylindrical hub 502. Film seal 580 is attached, e.g., by ultrasonic welding,
heat staking, laser welding, etc., to the upper surface of cylindrical hub 502 of
stir bar 500 to cover over void 578. It is preferred that film seal 580 have a seal
layer material that is chemically compatible with the material of stir bar 500.
[0116] FIGs. 44-46 show a configuration for a stir bar 500-1, having substantially the same
configuration as stir bar 500 discussed above with respect to FIGs. 40-43, with the
sole difference being that film seal 580 used to seal void 578 has been replaced with
a permanent cover 580-1. In this embodiment, cover 580-1 is unitary with the stir
bar body, which are formed around magnet 560 during the insert molding process.
[0117] While the stir bar embodiments of FIGs. 24-46 have been described as being for use
with microfluidic dispensing device 210 having guide portion 226, those skilled in
the art will recognize that stir bar 132 described above in relation to microfluidic
dispensing device 110 having guide portion 134 may be modified to also include a two-tiered
stir bar paddle design for use with guide portion 134.
[0118] When fluid is first introduced into the respective microfluidic dispensing device,
e.g., microfluidic dispensing device 210, the fluid is at a desired state of particulate
suspension having a mixed viscosity. This ideal condition is illustrated in FIG. 47.
In particular, FIG. 47 is an x-ray image of an implementation of microfluidic dispensing
device 210 of FIGs. 17-23 having a longitudinal extent of housing 212 arranged along
a vertical axis 600. FIG. 47 illustrates fluid 602 having suspended particulate content,
and with no accumulation of settled particulate, i.e., in an ideal state for use.
[0119] However, over time, the particulate portion of the fluid tends to separate from the
bulk liquid portion of the fluid. In turn, over time, the particulate portion tends
to accumulate as a settled particulate portion formed as a settled layer of particles.
In order to achieve coverage uniformity of the ejected fluid, it is desirable to maintain
the fluid at the desired state of particulate suspension in the fluid liquid by performing
fluid re-mixing operations.
[0120] It has been observed that the density of the bulk fluid liquid portion of the fluid
is less than the density of the settled particulate portion. Also, the dense settled
layer of the settled particulate portion will have a greater viscosity than the viscosity
of the desired mixed fluid. The separated fluid may also create re-mixing challenges
because the higher density of the settled particulate portion will tend to inhibit
the rotational motion of the stir bar.
[0121] FIG. 48 is an x-ray image of an implementation of microfluidic dispensing device
210 having the longitudinal extent of housing 212 arranged along a vertical axis 600,
with housing 212 oriented such that ejection chip 118 faces vertically upward and
with the planar extent of ejection chip 118 being substantially perpendicular to vertical
axis 600. Contained in housing 212 is stir bar 500 having magnet 560. Fluid reservoir
228 of microfluidic dispensing device 210 is shown to contain fluid 602 that includes
settled particulate 604 at a gravitational low region 606 of fluid reservoir 228.
In the orientation shown, ejection chip 118 is facing vertically upward, and the settled
particulate 604 has accumulated at the gravitational low region 606 of fluid reservoir
228 on the opposite end of housing 212 relative to ejection chip 118.
[0122] FIG. 49 is an x-ray image of an implementation of microfluidic dispensing device
210 tilted off-axis from vertical axis 600 by an angular amount 608 of about 20 to
25 degrees, and depicts how settled particulate 604 migrates to a new gravitational
low region 610 of fluid reservoir 228 based on the change of orientation of housing
212 relative to vertical axis 600. Also, it can be seen that the particulate layer
adjacent to the walls of fluid reservoir 228 do not tend to move easily by changing
the orientation of microfluidic dispensing device 210.
[0123] FIG. 50 is an x-ray image of an implementation of microfluidic dispensing device
210 (containing stir bar 224 having magnet 260; see also FIGs. 18 and 23) that illustrates
an undesirable orientation, wherein housing 212 is oriented such that ejection chip
118 faces vertically downward with the planar extent of ejection chip 118 being substantially
perpendicular to vertical axis 600. As shown, settled particulate 604 migrates to
a new gravitational low region 612 of fluid reservoir 228 based on the change of orientation
of housing 212, such that settled particulate 604 has accumulated over channel inlet
246-1 and channel outlet 246-2 of fluid channel 246. Thus, without sufficient mixing
of fluid 602, settled particulate 604 would render microfluidic dispensing device
210 inoperable, by completely blocking fluid channel 246, which in turn, would prevent
fluid from reaching ejection chip 118.
[0124] Referring to FIG. 51, microfluidic dispensing device 210 is shown in a Cartesian
space having X, Y, and Z axes, with the longitudinal extent of housing 212 lying on
the positive Z-axis and the lateral extent of housing 212 lying on the X-Y-plane.
In the X-Z plane, the positive X-axis represents 0 degrees; the Z-axis represents
vertical, with the upper Z-axis (positive) labeled as 90 degrees, corresponding to
vertical axis 600 discussed above; and the X-axis (negative) represents 180 degrees.
An orientation of the longitudinal extent of housing 212 of microfluidic dispensing
device 210 is represented by fluid ejection direction 120-1, and which also represents
the direction that ejection chip 118 and fluid channel 246 is facing.
[0125] In preparation for mixing, microfluidic dispensing device 210 may be positioned such
that fluid ejection direction 120-1 does not face downward. The term "not face downward"
means that the arrow of fluid ejection direction 120-1 does not point below the X-Y
plane, i.e., is never less than horizontal. Thus, in the orientation of the present
example, microfluidic dispensing device 210 may be rotated in the X-Z plane about
the Y-axis, in a range of upward vertical (Z+ at 90 degrees) plus or minus 90 degrees,
i.e., upward vertical to horizontal without the fluid ejection direction 120-1 being
pointed downward.
[0126] It is noted that the planar extent of ejection chip 118 is substantially perpendicular
to fluid ejection direction 120-1 in all orientations around fluid ejection direction
120-1, and the planar extent of base wall 230 of housing 212 of microfluidic dispensing
device 210 is substantially parallel to fluid ejection direction 120-1. Thus, the
direction of tilt of housing 212 (X+ or X-) in the X-Z plane (e.g., base wall 230
facing upwardly or facing downwardly) may determine the extent to which particulate
settlement may accumulate around stir bar 224.
[0127] In the illustration of FIG. 52, microfluidic dispensing device 210 is shown with
fluid ejection direction 120-1 pointing upwardly at 135 degrees (i.e., positive 45
degrees offset from 90 degrees (upward vertical)), and with microfluidic dispensing
device 210 oriented with an exterior 222-2 of dome portion 222-1 of diaphragm 222
facing upwardly and with an exterior 230-1 of base wall 230 facing downwardly. The
angle at which each of the exterior 222-2 of diaphragm 222 and the exterior 230-1
of base wall 230 is considered to face corresponds to the angle at which rotational
axis 250 of stir bar 224 intersects the upward vertical portion of the Z-axis, with
the exception of when rotational axis 250 of stir bar 224 is parallel to the Z-axis.
In the example of FIG. 52, the exterior 222-2 of dome portion 222-1 of diaphragm 222
is facing upwardly at 45 degrees and the exterior 230-1 of base wall 230 is facing
downwardly at 45 degrees. At the 135 degree orientation of fluid ejection direction
120-1 depicted in FIG. 52, any particulate settled or settling along base wall 230
will start to migrate toward a gravitational low point in fluid reservoir 228 and
away from stir bar 224 (see also FIG. 49).
[0128] Referring to FIG. 53, alternatively, an orientation of fluid ejection direction 120-1
may be in a range of 40 degrees to 90 degrees, and wherein when the orientation is
not vertical, i.e., not 90 degrees, the exterior 230-1 of base wall 230 is positioned
to face upwardly and the exterior 222-2 of diaphragm 222 is positioned to face downwardly.
In the specific example of FIG. 53, the orientation of microfluidic dispensing device
210 has the benefit of the nozzles-up orientation for ejection chip 118, but has the
exterior 222-2 of dome portion 222-1 of diaphragm 222 switched to face downwardly
at 45 degrees from vertical, and thus the exterior 230-1 of base wall 230, and correspondingly,
convex surface 276 of stir bar 224 that contacts base wall 230, now faces upwardly
at an angle of 45 degrees from vertical. The 45 degree orientation of microfluidic
dispensing device 210 will still move the particles away from ejection chip 118 and
fluid channel 26, but also will cause the particulate to settle in a region spaced
away from the plurality of paddles 252, 254, 256, 258 (see also FIG. 24) of stir bar
224 and towards the dome portion 222-1 of diaphragm 222. However, if stir bar 224
can be rotated, i.e., is not blocked from rotation by particulate sediment, then the
orientation depicted in FIG. 52 is preferred over the orientation depicted in FIG.
53, because in the orientation depicted in FIG. 52, the higher tip velocity of stir
bar 224 will be closer to the settled particulate than in the orientation of FIG.
53.
[0129] As a general observation, the longer the time between uses of the microfluidic dispensing
device or between re-mixing within the microfluidic dispensing device, the longer
the mixing time that will be required to re-mix the fluid in the microfluidic dispensing
device to achieve an acceptable level of particulate suspension, e.g., preferably,
a level within the tolerances of an initial filling of the microfluidic dispensing
device, as depicted in FIG. 47.
[0130] Referring to FIG. 54, there is shown a block diagram of external magnetic field generator
164 in accordance with an aspect of the present invention. External magnetic field
generator 164 includes a microcontroller 164-1, an electromagnetic field rotator 164-2,
an electromagnetic field generator 164-3, and a sensor 164-4. Microcontroller 164-1
includes a microprocessor, on-board non-transitory electronic memory 164-5, and interface
circuitry, e.g., input/output circuits, a universal asynchronous receiver/transmitter
(UART), analog-to-digital (A-to-D) converter, etc., as is known in the art. Microcontroller
164-1 is configured to execute program instructions to control the rotation of the
magnetic field generated by external magnetic field generator 164, and in turn, to
control the rotation of a stir bar, such as stir bar 224 having magnet 260.
[0131] More particularly, electromagnetic field generator 164-3 generates an external magnetic
field, which is coupled to magnet 260 of stir bar 224. Microcontroller 164-1 executes
program instructions to generate control signals that are supplied to electromagnetic
field rotator 164-2 to control a rotational speed and rotational direction of the
magnetic field generated by electromagnetic field generator 164-3, and in turn, to
control the rotational speed and rotational direction of stir bar 224. During normal
mixing operation, the rotational speed of stir bar 224 may be in a range, for example,
of 100 to 1000 revolutions per minute. As discussed above, the external magnetic field
generated by external magnetic field generator 164 may be rotated electronically,
akin to operation of a stepper motor, by positioned discrete electromagnets that are
selectively turned on and off to produce a virtual rotation of the magnetic field
and which can switch directions, or alternatively, may be physically rotated via a
magnetic plate, e.g., a permanent magnet, connected to a rotatable motor shaft.
[0132] In accordance with the present invention, sensor 164-4 has an electrical output that
provides a feedback signal, which is used to determine whether or not the stir bar,
e.g., stir bar 224, is rotating properly and efficiently within the fluid reservoir
of the microfluidic dispensing device, e.g., microfluidic dispensing device 210. Sensor
164-4 may be, for example, a Hall-effect sensor, which generates and supplies a composite
magnetic signal, in electrical form, based on the relative angular rotational position
of magnet 260 of stir bar 224 and the position of the rotating magnetic field generated
by electromagnetic field rotator 164-2 and electromagnetic field generator 164-3 of
external magnetic field generator 164.
[0133] In the present embodiment, the control of the rotation of stir bar 224 is equivalent
to driving a stepper motor. The angular rotational velocity of stir bar 224 must match
the average angular rotational velocity magnetic field generated electromagnetic field
rotator 164-2 and electromagnetic field generator 164-3, or else the rotational motion
of stir bar 224 will "break phase" with the rotating magnetic field generated by electromagnetic
field rotator 164-2 and electromagnetic field generator 164-3. As used herein, each
of the terms "break phase", "breaking phase" and "broken phase" refers to a condition
wherein the angular rotational velocity of the rotating magnetic field exceeds the
angular rotational velocity of the stir bar, e.g., stir bar 224 having magnet 260.
[0134] In accordance with the present invention, the rotating magnetic field may be analog,
as in a continuous rotation, or may be digital, as in predefined incremental angular
positions.
[0135] To illustrate these concepts, please refer also to FIGs. 55-58. In each of FIGs.
55-58, both the rotational direction of a rotating magnetic field 700 generated by
electromagnetic field rotator 164-2 and electromagnetic field generator 164-3 of external
magnetic field generator 164, and the rotational direction of magnet 260 of stir bar
224, is in rotational direction 250-1, i.e., a counterclockwise as shown. Magnet 260
includes a north pole (N) and a south pole (S). Also, the rotating magnetic field
700 generated by electromagnetic field generator 164-3 and electromagnetic field rotator
164-2 has a north pole (N) and a south pole (S).
[0136] FIG. 55 illustrates stir bar 224 having magnet 260 relative to the angular rotational
position of magnetic field 700 generated by electromagnetic field generator 164-3
and electromagnetic field rotator 164-2 of external magnetic field generator 164.
In the present example, magnetic field 700 is depicted at four discrete angular rotational
positions, individually identified as Position 1, Position 2, Position 3, and Position
4. While in the present example only four angular rotational positions are identified
for ease of illustration, those skilled in the art will recognize that in practice,
the number of angular rotational positions may be increased, if desired, and may correspond
in number to 2 x n, wherein n is a positive integer. In FIG. 55, an initial occurrence
of Position 1 is identified as position P1(A), and it is to be understood that the
respective N, S depictions of the angular rotational position of magnetic field 700
of position P1(A) and position P1 are identical. As the angular rotational position
of magnetic field 700 generated by electromagnetic field generator 164-3 and electromagnetic
field rotator 164-2 is rotated, the angular rotational position of magnet 260 of stir
bar 224 attempts to follow, since unlike poles attract and like poles repel.
[0137] Referring to FIG. 55, position P1(A), if magnetic field 700 of electromagnetic field
generator 164-3 is stationary and stir bar 224 is not obstructed from rotation, magnet
260 of stir bar 224 will lock onto the angular rotational position of magnetic field
700 generated by electromagnetic field generator 164-3, e.g., the north pole (N) of
magnet 260 of stir bar 224 will be attracted to the south pole (S) of magnetic field
700 generated by electromagnetic field generator 164-3 of external magnetic field
generator 164.
[0138] In FIG. 55, for example, positions P1(A), P2, P3, P4, and P1 depict a complete rotation
of magnetic field 700 of electromagnetic field generator 164-3 and electromagnetic
field rotator 164-2 from the stationary position P1(A), and a complete rotation of
stir bar 224, at discrete sample times. As depicted in positions P1, P2, P3, and P4,
the angular rotational position of magnet 260 of stir bar 224 may lag in phase from
the angular rotational position of the rotating magnetic field 700 generated by electromagnetic
field generator 164-3 and electromagnetic field rotator 164-2 of external magnetic
field generator 164. Some phase lag is expected.
[0139] In the present embodiment, a range of normal phase lag (e.g., determined empirically)
is defined, wherein the amount of phase lag does not adversely affect the rotational/stirring
efficiency of stir bar 224. In the present example, the range of normal phase lag
may be defined as a range of 0 degrees through 140 degrees. As such, a phase lag that
is not normal is considered to be an abnormal phase lag, which in the present example,
is a phase lag of more than 140 degrees. The abnormal phase lag will include the condition
of breaking phase, and also is inclusive of the special case of breaking phase of
a stuck stir bar.
[0140] In the present example of FIG. 55, the phase lag is approximately 30 degrees. As
used herein, the term "approximately" means the indicated amount plus or minus 10
percent. Continuous rotation of stir bar 224 by the rotation of magnetic field 700
may be recognized by the repetition of the sequential positions P1, P2, P3, and P4.
[0141] FIG. 56 illustrates a scenario wherein the torque required to rotate stir bar 224
is too high to begin rotation, i.e., stir bar 224 is stuck and prevented from rotation,
such as for example, by an accumulation of settled particulate around stir bar 224.
As such, as illustrated at the sequence of positions P1-4, representing a completed
rotation of magnetic field 700, stir bar 224 is stationary while magnetic field 700
of external magnetic field generator 164 is rotating. Thus, FIG. 56 illustrates one
example wherein stir bar 224 has broken phase from the rotation of magnetic field
700 generated by electromagnetic field generator 164-3 of external magnetic field
generator 164.
[0142] Another possible case where stir bar 224 would break phase from the rotating magnetic
field 700 is when the acceleration rate of the angular rotational velocity of the
rotation of magnetic field 700 provided by electromagnetic field rotator 164-2 and
electromagnetic field generator 164-3 is faster than can be obtained by stir bar 224.
In such a case, for example, the present angular rotational velocity of magnetic field
700 must be decreased such that an acceptable phase lag relationship may be obtained.
[0143] FIG. 57 illustrates a scenario wherein there is a phase lag of approximately 45 degrees
between the angular rotational position of stir bar 224 and the angular rotational
position of magnetic field 700 at each of the plurality of positions P1-P4 of the
rotating magnetic field 700.
[0144] FIG. 58 illustrates a scenario wherein there is a phase lag of approximately 90 degrees,
represented by an arced arrowed line, between the angular rotational position of stir
bar 224 and the angular rotational position of magnetic field 700 at each of the plurality
of positions P1-P4 of the rotating magnetic field 700. Also, FIG. 58 demonstrates
a plurality of rotational cycles, with each rotational cycle including a respective
set of positions P1-P4. It is noted that for purposes of illustration clarity, only
magnet 260 of stir bar 224 is shown in FIG. 58, and due to size restrictions in FIG.
58, the north pole (N) of magnet 260 is represented by a bold dot.
[0145] Referring again to FIGs. 56-58, each of FIGs. 56-58 include three graphs, including
a stir bar magnet strength (top graph), a magnetic field strength (middle graph) of
magnetic field 700, and a composite magnetic strength (lower graph), relative to the
four angular rotational positions P1, P2, P3 and P4 of magnetic field 700 under the
various scenarios of FIGs. 56-58. The vertical axis of each of the graphs represents
a magnetic strength amplitude and the horizontal axis represents an angular rotational
position, wherein the scale 0 to 1 on the horizontal axis represents one complete
revolution (cycle) of magnetic field 700, corresponding to positions P1-P4 of magnetic
field 700. FIG. 58 depicts multiple revolutions (cycles) of magnetic field 700, wherein
each of the ranges 0-1, 1-2, 2-3, 3-4 represents one revolution of magnetic field
700. The composite magnetic strength (bottom graph) is an algebraic sum of the stir
bar magnet strength (top graph) and the magnetic field strength (middle graph) at
any point along the horizontal axis, and is representative of the electrical output
of sensor 164-4, as a Hall Effect sensor, which receives magnetic contributions from
both of the stir bar magnet 260 and magnetic field 700 during operation.
[0146] In general, it is noted that in FIGs. 56-58, the magnetic field strength profile
(curve) of the magnetic field strength (middle) graph is a square wave, and will have
the same profile shape, regardless of the angular rotational velocity of magnetic
field 700, due to the fixed location of sensor 164-4 with respect to the rotating
magnetic field 700. As such, variations in the respective shapes of the composite
magnetic strength profile of the composite magnetic strength (bottom) graph as between
FIGs. 56-58 are due to differences in the amount that the angular rotational position
of magnet 260 of stir bar 224 lags the angular rotational position of magnetic field
700. Thus, by comparing the present output of sensor 164-4 representing a present
composite magnetic strength profile with a previously stored profile database, i.e.,
an electronic library, of composite magnetic strength profiles, a determination may
be made as to whether the stir bar is stuck, whether operating normally, i.e., within
a predefined range of lag, or whether the stir has broken phase with the rotating
magnetic field.
[0147] As introduced above, FIG. 56 depicts a scenario wherein stir bar 224, and in turn
magnet 260, are stuck, i.e., blocked from rotation. FIG. 56 includes the three graphs
described above, including a stir bar magnet strength profile 702 of magnet 260, a
magnetic field strength profile 704 of magnetic field 700, and a composite magnetic
strength profile 706. If desired, the stir bar magnet strength profile 702, representing
a stuck stir bar, may be generated at the sensor output of sensor 164-4, for example,
by taking a magnetic reading in the absence of magnetic field 700, e.g., magnetic
field 700 of external magnetic field generator 164 is turned OFF. Also, if desired,
the magnetic field strength profile 704 having a constant square wave shape, may be
generated at the sensor output of sensor 164-4, for example, in the absence of microfluidic
dispensing device 210 or in the presence of microfluidic dispensing device 210 with
stir bar 224 blocked from rotation.
[0148] The composite magnetic strength profile 706 is the algebraic sum of the stir bar
magnet strength profile 702 and the magnetic field strength profile 704. Since the
stir bar magnet strength profile 702 (stuck stir bar) is a constant at unity, representing
a non-rotation of stir bar magnet 260, then the shape of the composite magnetic strength
profile 706 is the same as that of the magnetic field strength profile 704 of magnetic
field 700 but for a vertical shift of unity on the vertical axis. Moreover, the composite
magnetic strength profile 706 may be generated at the sensor output of sensor 164-4
by rotating magnetic field 700 while rotation of magnet 260 of stir bar 224 is blocked.
[0149] As such, referring again also to FIG. 54, the composite magnetic strength profile
706 generated by sensor 164-4 is supplied as a composite electrical signal to microcontroller
164-1, which in turn processes the composite electrical signal, e.g., through an analog-to-digital
converter, and stores digital data representative of the composite magnetic strength
profile 706, stuck stir bar, in a profile database 164-6 formed in electronic memory
164-5 of microcontroller 164-1 of external magnetic field generator 164. Thus, the
digital representation of the composite magnetic strength profile 706 may be retrieved
from the profile database 164-6 of electronic memory 164-5 for future reference as
being representative of a stuck stir bar condition of stir bar 224 of microfluidic
dispensing device 210. Accordingly, the composite magnetic strength profile 706 may
be used by microcontroller 164-1 to aid in determining the operational status (e.g.,
stuck, normal, breaking phase, etc.) of stir bar 224 relative to the rotation of the
rotating magnetic field 700 generated by external magnetic field generator 164.
[0150] Similarly, an electrical signal generated by sensor 164-4 representative of the magnetic
field strength profile 704 may be processed by microcontroller 164-1, e.g., through
an analog-to-digital converter, which in turn stores digital data representative of
the magnetic field strength profile 704 in profile database 164-6 formed in electronic
memory 164-5 of microcontroller 164-1 for future reference.
[0151] As introduced above, FIG. 57 illustrates a scenario wherein there is a phase lag
of approximately 45 degrees between the angular rotational position of magnet 260
of stir bar 224 and the angular rotational position of magnetic field 700 at each
of the plurality of positions P1-P4 of the rotating magnetic field 700. FIG. 57 includes
the three types of graphs described above, including a stir bar magnet strength profile
708 of magnet 260, the magnetic field strength profile 704 of magnetic field 700,
and a composite magnetic strength profile 710.
[0152] To establish the composite magnetic strength profile 710 representing a 45 degree
lag, the 45 degree lag condition may be simulated in a lab setting, and then a reading
of the sensor output of sensor 164-4 is taken to acquire the composite electrical
signal representative of the composite magnetic strength profile 710. In particular,
referring also to FIG. 54, the composite magnetic strength profile 710 generated by
sensor 164-4 is supplied as a composite electrical signal to microcontroller 164-1,
which in turn processes the composite electrical signal, e.g., through an analog-to-digital
converter, and stores digital data representative of the composite magnetic strength
profile 710, 45 degree lag, in profile database 164-6 formed in electronic memory
164-5 of microcontroller 164-1 of external magnetic field generator 164. Thus, the
digital representation of the composite magnetic strength profile 710 also may be
retrieved from the profile database 164-6 of electronic memory 164-5 for future reference
as being representative of a 45 degree lag of magnet 260 of stir bar 224 of microfluidic
dispensing device 210 relative to the rotating magnetic field 700. In turn, the composite
magnetic strength profile 710 may be used by microcontroller 164-1 in determining
the operational status (e.g., stuck, normal, breaking phase, etc.) of stir bar 224
relative to the rotation of the rotating magnetic field 700 generated by external
magnetic field generator 164.
[0153] If desired, the stir bar magnet strength profile 708 of magnet 260 may most easily
be derived by subtracting the magnetic field strength profile 704 of magnetic field
700, having the constant square wave shape, from the composite magnetic strength profile
710. This mathematical operation may be carried out by program instructions executed
by microcontroller 164-1, which in turn may also store the stir bar magnet strength
profile 708 of magnet 260 in profile database 164-6 formed in electronic memory 164-5
of microcontroller 164-1.
[0154] As introduced above, FIG. 58 illustrates a scenario wherein there is a phase lag
of approximately 90 degrees between the angular rotational position of stir bar 224
and the angular rotational position of magnetic field 700 at each of the plurality
of positions P1-P4 of the rotating magnetic field 700. FIG. 58 includes the three
types of graphs described above, including a stir bar magnet strength profile 712
of magnet 260, the magnetic field strength profile 704 of magnetic field 700, and
a composite magnetic strength profile 714. As a general observation, as the angular
rotational velocity of stir bar 224 is increased, there will be an increase in the
amount of phase lag between the angular rotational position of stir bar 224 and the
angular rotational position of magnetic field 700.
[0155] To establish the composite magnetic strength profile 714 representing a 90 degree
lag, the 90 degree lag condition may be simulated in a lab setting, and then a reading
of the sensor output of sensor 164-4 is taken to acquire the composite electrical
signal representative of the composite magnetic strength profile 714. In particular,
referring also to FIG. 54, the composite magnetic strength profile 714 generated by
sensor 164-4 is supplied as a composite electrical signal to microcontroller 164-1,
which in turn processes the composite electrical signal, e.g., through an analog-to-digital
converter, and stores digital data representative of the composite magnetic strength
profile 714, having a 90 degree lag, in profile database 164-6 formed in electronic
memory 164-5 of microcontroller 164-1 of external magnetic field generator 164.
[0156] Thus, the digital representation of the composite magnetic strength profile 714 also
may be retrieved from the profile database 164-6 of electronic memory 164-5 for future
reference as being representative of a 90 degree lag of magnet 260 of stir bar 224
of microfluidic dispensing device 210 relative to the rotating magnetic field 700.
In turn, the composite magnetic strength profile 714 may be used by microcontroller
164-1 in determining the operational status (e.g., stuck, normal, breaking phase,
etc.) of stir bar 224 relative to the rotation of the rotating magnetic field 700
generated by external magnetic field generator 164.
[0157] If desired, the stir bar magnet strength profile 712 of magnet 260 may most easily
be derived by subtracting the magnetic field strength profile 704 of magnetic field
700, having the constant square wave shape, from the composite magnetic strength profile
714. This mathematical operation may be carried out by program instructions executed
by microcontroller 164-1, which in turn may also store the stir bar magnet strength
profile 712 of magnet 260 in profile database 164-6 formed in electronic memory 164-5
of microcontroller 164-1.
[0158] In accordance with the above description, composite magnetic strength profiles are
stored in profile database 164-6 of electronic memory 164-5, which may be representative
of a normal condition and a stuck stir bar condition. The stuck stir bar condition
may be represented by a single composite magnetic strength profile, such as composite
magnetic strength profile 706 of FIG. 56. The normal condition may be represented
by a plurality of composite magnetic strength profiles that are in the preestablished
range of normal phase lag, such as for example, a range of 0 degrees through 140 degrees.
[0159] In the example of FIGs. 57 and 58, the composite magnetic strength profile 710 representing
a phase lag of 45 degrees and the composite magnetic strength profile 714 representing
a phase lag of 90 degrees may be two of the plurality of composite magnetic strength
profiles that are representative of a normal phase lag. For example, the normal phase
lag may be represented by any number of composite magnetic strength profiles that
are in the designated normal lag range. For example, the plurality of composite magnetic
strength profiles representative of the normal phase lag may be established at angular
increments, such as 1 degree increments, 5 degrees increments, or 10 degree increments,
or other such types of increments, and stored in the profile database 164-6 of electronic
memory 164-5.
[0160] Any composite magnetic strength profile read by sensor 164-4 that does not fall into
the normal phase lag range by default is an abnormal phase lag, wherein a stuck stir
bar is a special case of an abnormal lag condition. Thus, the normal phase lag range
(representative of a normal condition) and the abnormal phase lag (representative
of an abnormal condition) are mutually exclusive.
[0161] FIG. 59 is a flowchart of a method of operating a stir bar in a fluidic dispensing
device, in accordance with an aspect of the present invention, with further reference
to the embodiment of FIGs. 17-27, including stir bar 224. The method of FIG. 59, except
for any manual intervention at step S810, may be performed by program instructions
executed by microcontroller 164-1, depicted in FIG. 54.
[0162] At step S800, it is determined whether the present phase lag between the angular
rotational position of the magnet 260 of stir bar 224 and the angular rotational position
of magnetic field 700 generated by electromagnetic field rotator 164-2 and electromagnetic
field generator 164-3 of external magnetic field generator 164 is in a range of normal
phase lag.
[0163] In particular, in real time, sensor 164-4 provides electronic signals representative
of a present composite magnetic strength of magnet 260 and magnetic field 700. Microcontroller
164-1 processes the electronic signals representative of a present composite magnetic
strength to acquire a present composite magnetic strength. Microcontroller 164-1 then
accesses profile database 164-6 of electronic memory 164-5 to compare the present
composite magnetic strength to the stored plurality of composite magnetic strength
profiles. If the comparison results in a match, or if the present composite magnetic
strength, e.g., curve, falls between two of the stored composite magnetic strength
profiles in the range of normal phase lag, then the phase lag between the angular
rotational position of the magnet 260 of stir bar 224 and the angular rotational position
of magnetic field 700 is in a range of normal phase lag, and stir bar 224 is considered
to be operating in a normal condition, resulting in a determination of YES. Otherwise,
the phase lag between the angular rotational position of the magnet 260 of stir bar
224 and the angular rotational position of magnetic field 700 is not in a range of
normal phase lag, resulting in a determination of NO, and is considered an abnormal
condition.
[0164] If the determination of step S800 is YES, then the process proceeds to step S802.
Steps S802, S804, and S806 are directed to improving the stirring efficiency of stir
bar 224 under the scenario that the phase lag is in a range of normal phase lag.
[0165] At step S802, it is determined whether the phase lag between the angular rotational
position of the magnet 260 of stir bar 224 and the angular rotational position of
magnetic field 700 is stable over time. As used herein, the phase lag is "stable"
if a group of consecutive readings of the present composite magnetic strength from
sensor 164-4 do not deviate from one another by more than a predetermined deviation,
such as for example, by more than 5 percent.
[0166] If the determination at step S802 is YES, i.e., that the phase lag is stable, then
at step S804, the angular rotational velocity of stir bar 224 is increased by increasing
the angular rotational velocity of the rotating magnetic field 700. To help avoid
a positive overshoot in angular rotational velocity, the increase will be gradual,
and may be incremental, e.g., in speed increase increments of one percent. In particular,
microcontroller 164-1 executes program instructions to determine whether the phase
lag is stable, and if so, then sends a signal to electromagnetic field rotator 164-2
to increase the angular rotational velocity of magnetic field 700 by the specified
amount. The process then returns to step S800.
[0167] If the determination at step S802 is NO, i.e., that the phase lag is not stable,
then at step S806 the angular rotational velocity of the rotating magnetic field 700
is decreased. To help avoid a negative overshoot in angular rotational velocity, the
decrease in the angular rotational velocity will be gradual, and may be incremental,
e.g., in speed decrease increments of one percent. In particular, microcontroller
164-1 executes program instructions to determine whether the phase lag is stable,
and if not, then sends a signal to electromagnetic field rotator 164-2 to decrease
the angular rotational velocity of magnetic field 700 by the specified amount. The
process then returns to step S800.
[0168] If the determination at step S800 is NO, i.e., the phase lag between the angular
rotational position of the magnet 260 of stir bar 224 and the angular rotational position
of magnetic field 700 is not in a range of normal phase lag, i.e., the phase lag is
abnormal, then the process proceeds to step S808.
[0169] Steps S808, S810, and S812 are invoked under the scenario that the phase lag is not
a range of normal phase lag, i.e., the phase lag is abnormal.
[0170] At step S808, it is determined whether stir bar 224 is stuck, i.e., stir bar 224
will not rotate.
[0171] In particular, in real time, sensor 164-4 provides electronic signals representative
of a present composite magnetic strength of magnet 260 and magnetic field 700. Microcontroller
164-1 processes the electronic signals representative of a present composite magnetic
strength to acquire a present composite magnetic strength. Microcontroller 164-1 then
accesses the stuck stir bar composite magnetic strength profile, e.g., composite magnetic
strength profile 706, from profile database 164-6 of electronic memory 164-5 to compare
the present composite magnetic strength to the stored stuck stir bar composite magnetic
strength profile.
[0172] If the comparison results in a match, then the result at step S808 is YES, indicating
a stuck stir bar, i.e., the special case of an abnormal phase lag between the angular
rotational position of the magnet 260 of stir bar 224 and the angular rotational position
of magnetic field 700. If the comparison does not result in a match, then the result
at step S808 is NO, and the phase lag is considered to be a general case of abnormal
phase lag, and the process proceeds to step S812.
[0173] If the determination at step S808 is YES, that stir bar 224 is stuck, then the process
proceeds to S810, wherein a user intervention may be invoked to unstick the stuck
stir bar. It has been observed that changing the orientation of microfluidic dispensing
device to use gravity to move the particulate and break up the layer formed by settled
particulate, such as settled particulate 604 of FIGs. 48-50, may be used to free a
stir bar, such as stir bar 224, which is stuck from rotation by the accumulated settled
particulate 604. In this regard, please see the discussion above with respect to FIGs.
47-53. It is noted that shallow ejection chip angles will not be able to use gravity
as effectively in moving sediment that may have settled in the ejection chip region
including the fluid channel, such as for example, during a shipping condition.
[0174] A further option in attempting to break up the layer formed by settled particulate,
such as settled particulate 604 depicted in FIG. 50, may be obtained by vibrating
microfluidic dispensing device 210. Such haptic vibration may also help to clear the
fluid channel, e.g., fluid channel 246 of FIGs. 48-50, and may be induced automatically
upon occurrence of the YES determination at step S808. The frequency and intensity
of the haptic vibration may be determined empirically, and may be dependent, at least
in part, on the amount of particulate in the fluid.
[0175] Following intervention at step S810, the process is returns to step S800.
[0176] If the determination at step S808 is NO, that stir bar 224 is not stuck, then the
assumption is made that the abnormal phase lag is due to some other cause, such as
due to the magnet 260 of stir bar 224 breaking phase with the rotating magnetic field
700 provided by electromagnetic field rotator 164-2 and electromagnetic field generator
164-3, and the process proceeds to step S812.
[0177] At step S812, the angular rotational velocity of rotating magnetic field 700 is decreased.
To help avoid a negative overshoot in the correction of the angular rotational velocity
of rotating magnetic field 700, the decrease in angular rotational velocity will be
gradual, and may be incremental, e.g., in speed decrease increments of one percent.
In particular, microcontroller 164-1 executes program instructions to decrease the
angular rotational velocity of magnetic field 700 by the specified amount. For example,
the angular rotational velocity of the rotating magnetic field 700 is decreased until
the normal phase lag associated with steps S800 through S804 is again achieved. Following
step S812, the process returns to step S800.
[0178] It is contemplated that the determination made at step S800 may be simplified to
a predefined number of conditions, such as for example, a normally operating stir
bar, a stuck stir bar, and a stir bar that has broken phase with the rotating magnetic
field, wherein steps S800 and S808 may be essentially combined into a single step
having three possible outcomes.
[0179] Also, from the information obtained above, an estimate of viscosity of the mixed
or unmixed fluid is possible by correlating the phase lag or peak angular rotational
velocity of stir bar 224 with various levels of viscosity, e.g., by empirically establishing
a viscosity curve, and comparing the present phase lag or peak angular rotational
velocity of stir bar 224 with the viscosity curve. For a digitally changing magnetic
field 700, a step response signal, e.g., step-wise increasing the angular rotational
velocity of magnetic field 700, may also be used to determine an estimate of fluid
viscosity in microfluidic dispensing device 210.
[0180] Further, it is contemplated that additional sensors, like sensor 164-4, e.g., additional
Hall Effect sensors, may be used to further improve signal detection and profile generation.
Also, it is noted that for the more analog rotating magnetic fields, a digital Hall
Effect sensor can be used to look at the time periods instead of amplitudes in generating
the composite magnetic strength profiles.
[0181] As an alternative to the above method using a Hall Effect sensor as sensor 164-4,
it is contemplated that sensor 164-4 may be a vibration sensor. A vibration sensor
will generate different signal signatures from the composite magnetic strength profile
generated by a Hall Effect sensor, and rather, the vibration sensor directly generates
an electronic vibration profile that may be substituted for the composite magnetic
strength profile in the method described above. In such a case, the vibration sensor
(acceleration, velocity, or positional) measures the differences caused by changes
in magnetic attraction and repulsion between magnet 260 of stir bar 224 and the rotating
magnetic field 700.
[0182] For example, if magnet 260 of stir bar 224 is rotating normally, the phase lag between
magnet 260 of stir bar 224 and magnetic field 700 results in sensor 164-4, as a vibration
sensor, generating a fairly uniform vibration signal because the magnet attraction,
and thus the phase lag, during rotation is stable (see also step S802 described above).
[0183] In an abnormal phase lag condition of a loss of phase, there is a periodic repulsion
of magnet 260 of stir bar 224 and magnetic field 700 that results in sensor 164-4,
as a vibration sensor, generating a corresponding vibration pulse parallel to the
axis of rotation, e.g., is strongest each time a pole of magnet 260 of stir bar 224
coincides with a like pole of magnetic field 700. In this condition, the stir bar
is rotating erratically and inefficiently.
[0184] In a stir bar stuck condition, there the periodic repulsion of magnet 260 of stir
bar 224 and magnetic field 700 occurs once per revolution, sensor 164-4 (as a vibration
sensor) will generate the strongest signal parallel to the axis of rotation.
[0185] Notwithstanding the use of a stir bar to generate a fluid flow within a fluidic dispensing
device to produce a remixing of the fluid contained in the fluidic dispensing device,
it has been recognized that in a fluid channel of a fluidic dispensing device there
is a potential for stagnation zones to be created, wherein settled particulate is
not affected by the fluid flow through the fluid channel and/or a fluid flow through
the fluid channel may result in an unintentional depositing of particulate. Such stagnation
zones may be created, for example, at locations in the fluid channel where there are
abrupt changes in the surface features, such as in a corner defined by orthogonal
planar surfaces.
[0186] FIG. 60 is a further enlarged portion of the view depicted in FIG. 23. As shown in
FIG. 60, fluid channel 246 defines a passage 246-6, represent by a dashed arrowed
line, which extends between channel inlet 246-1 and channel outlet 246-2. Stir bar
224, when rotated, generates a fluid flow into channel inlet 246-1, through passage
246-6, and out of channel outlet 246-2.
[0187] Passage 246-6 has an outer wall structure 246-7 and an inner wall structure 246-3,
246-4, 246-5 formed by convexly arcuate wall 246-3 and transition radii 246-4, 246-5.
Outer wall structure 246-7 is spaced away from inner wall structure 246-3, 246-4,
246-5.
[0188] Outer wall structure 246-7 includes an inlet side wall 650, an outlet side wall 652,
and a distal wall portion 654. Outlet side wall 652 is spaced away from inlet side
wall 650. Distal wall portion 654 is interposed between inlet side wall 650 and outlet
side wall 652. Inlet side wall 650 is substantially perpendicular to distal wall portion
654 to define a first corner structure 246-8 that forms a first stagnation zone 656
of passage 246-6. Outlet side wall 652 is substantially perpendicular to distal wall
portion 654 to define a second corner structure 246-9 that forms a second stagnation
zone 658 of passage 246-6. Referring also to FIG. 18, fluid opening 232-3 extends
through exterior wall 232-1 to distal wall portion 654 of fluid channel 246 between
first corner structure 246-8, i.e., the first stagnation zone 656 and second corner
structure 246-9, i.e., the second stagnation zone 658.
[0189] Referring to FIGs. 60-63, flow control portion 286, as a unitary component having
flow separator feature 286-1, flow rejoining feature 286-2, and concavely arcuate
surface 286-3, further includes an inlet flow director member 660 positioned adjacent
to channel inlet 246-1 and an outlet flow director member 652 positioned adjacent
to channel outlet 246-2. Inlet flow director member 660 is a portion of inlet fluid
port 242 of chamber 238 and outlet flow director member 662 is a portion of outlet
fluid port 244 of chamber 238.
[0190] More particularly, inlet fluid port 242 of chamber 238 is defined by an interior
perimetrical wall portion 240-4 of interior perimetrical wall 240 in opposed combination
with an inlet port wall portion 286-4 of flow separator feature 286-1 and inlet flow
director member 6600. Interior perimetrical wall portion 240-4 of interior perimetrical
wall 240 and inlet flow director member 660 are oriented to laterally converge in
a direction toward channel inlet 246-1 of fluid channel 246. Conversely, outlet fluid
port 244 of chamber 238 is defined by an interior perimetrical wall portion 240-5
of interior perimetrical wall 240 in opposed combination with an outlet port wall
portion 286-5 of flow rejoining feature 286-2 of flow control portion 286 and outlet
flow director member 662. Interior perimetrical wall portion 240-5 of interior perimetrical
wall 240 and outlet flow director member 662 are oriented to laterally diverge in
a fluid flow direction away from channel outlet 246-2.
[0191] Referring also to FIGs. 61-63, inlet port wall portion 286-4 of flow separator feature
286-1 of flow control portion 286 has a proximal end 664-1, a distal end 664-2, and
a first height 664-3 (FIG. 62). The proximal end 664-1 of inlet port wall portion
286-4 is located to intersect concavely arcuate surface 286-3 at an acute angle to
form a first apex 664-4 (see FIG. 61). Likewise, outlet port wall portion 286-5 of
flow rejoining feature 286-2 of flow control portion 286 has a proximal end 666-1,
a distal end 666-2, and a height 666-3 (FIG. 63). The proximal end 666-1 of the outlet
port wall portion 286-5 is located to intersect concavely arcuate surface 286-3 at
a second acute angle to form a second apex 666-4 (see FIG. 61). The entire curvature
of concavely arcuate surface 286-3 extends between first apex 664-4 and second apex
666-4.
[0192] Inlet flow director member 660 has a surface structure having an inlet deflection
wall portion 660-1 that directs a portion of the fluid flow toward first corner structure
246-8, i.e., the first stagnation zone 656, in passage 246-6. Inlet deflection wall
portion 660-1 has a proximal end 660-2, a distal end 660-3, and a height 660-4. The
proximal end 660-2 of inlet deflection wall portion 660-1 is located to intersect
inlet port wall portion 286-4 of flow separator feature 286-1 at an obtuse angle.
[0193] As shown in FIG. 62, height 614-3 of inlet port wall portion 286-4 of flow separator
feature 286-1 is greater than the height 660-4 of inlet deflection wall portion 660-1
to further define the surface structure of inlet flow director member 660 to include
a first inlet ceiling portion 660-5 having a triangular shape and a second inlet ceiling
portion 660-6 having a trapezoidal shape. First inlet ceiling portion 660-5 is positioned
to laterally extend from inlet deflection wall portion 660-1 to inlet port wall portion
286-4 of flow control portion 286. Second inlet ceiling portion 660-6 is positioned
to laterally extend from inlet deflection wall portion 660-1 of inlet flow director
member 660 to inlet port wall portion 286-4 of flow control portion 286. Second inlet
ceiling portion 660-6 is positioned to distally extend from first inlet ceiling portion
660-5, and with second inlet ceiling portion 660-6 and first inlet ceiling portion
660-5 positioned to intersect at an obtuse angle.
[0194] Referring again to FIGs. 61-63, outlet flow director member 662 has a second surface
structure that facilitates generation of one or more eddy currents at second corner
structure 246-9, i.e., the second stagnation zone 668, near channel outlet 246-2.
In the present embodiment, the second surface structure of outlet flow director member
662 is symmetrical with the first surface structure of inlet flow director member
660 structure with respect to chamber 238, as well as with respect to channel mid-point
248. Outlet flow director member 662 has a second outlet wall portion 662-1 having
a proximal end 662-2, a distal end 662-3, and height 662-4. The proximal end 662-2
of second outlet wall portion 662-1 is located to intersect the outlet port wall portion
286-5 of flow rejoining feature 286-2 at a second obtuse angle.
[0195] As shown in FIG. 63, height 666-3 of outlet port wall portion 286-5 of flow separator
feature 286-1 is greater than the height 612-4 of second outlet deflection wall portion
662-1 to further define the surface structure of outlet flow director member 662 to
include a first outlet ceiling portion 662-5 having a triangular shape and a second
outlet ceiling portion 662-6 having a trapezoidal shape. The first outlet ceiling
portion 662-5 of outlet flow director member 662 is positioned to laterally extend
from the second outlet wall portion 662-1 to the outlet port wall portion 286-5 of
flow rejoining feature 286-2. The second outlet ceiling portion is positioned to laterally
extend from the second outlet wall portion to the outlet port wall portion 286-5.
The second outlet ceiling portion is positioned to distally extend from the first
outlet ceiling portion and with the second outlet ceiling portion and the first outlet
ceiling portion positioned to intersect at an obtuse angle.
[0196] FIGs. 64-71 are directed to still another embodiment for reducing the potential for
stagnation zones in a fluid channel of a fluidic dispensing device, such as a microfluidic
dispensing device 750. The present embodiment utilizes modifications to the wall structure
of the chamber so as to reduce the occurrence of abrupt changes in the surface features
and/or reducing the lateral extent of any orthogonal walls in the fluid channel region
of the fluidic dispensing device.
[0197] Microfluidic dispensing device 750 generally includes a housing 752 and a TAB circuit
which includes ejection chip 118, such as TAB circuit 114 described above, and which
for brevity will not be repeated here. Microfluidic dispensing device 750 is configured
to contain a supply of a fluid, such as a fluid containing particulate material. The
fluid may be, for example, cosmetics, lubricants, paint, ink, etc.
[0198] Referring to FIGs. 64 and 65, housing 752 includes a body 754 and a lid 756. Referring
also to FIGs. 67, 69, and 70, contained within housing 752 is a diaphragm 758 and
a stir bar 760 (see also FIG. 66). Each of the housing 752 components (body 754 and
lid 756) and stir bar 760 may be made of plastic, using a molding process. Diaphragm
758 is made of rubber, using a molding process.
[0199] In general, a fluid (not shown) is contained in a sealed region, i.e., a fluid reservoir
762, between body 754 and diaphragm 758. Stir bar 760 resides in the sealed fluid
reservoir 762 between body 754 and diaphragm 758 that contains the fluid. An internal
fluid flow may be generated within fluid reservoir 762 by rotating stir bar 760 so
as to provide fluid mixing and redistribution of particulate in the fluid within the
sealed region of fluid reservoir 762.
[0200] Referring now also to FIGs. 66-70, body 704 of housing 752 has a base wall 764 and
an exterior perimeter wall 766 contiguous with base wall 764. Exterior perimeter wall
766 is oriented to extend from base wall 764 in a direction that is substantially
orthogonal to base wall 764. As best shown in FIGs. 67, 69, and 70, lid 756 is configured
to engage exterior perimeter wall 766. Thus, exterior perimeter wall 766 is interposed
between base wall 764 and lid 756, with lid 756 being attached to the open free end
of exterior perimeter wall 766 by weld, adhesive, or other fastening mechanism, such
as a snap fit or threaded union. Attachment of lid 756 to body 754 occurs after installation
of stir bar 760 and diaphragm 758.
[0201] Referring to FIGs. 69-71, exterior perimeter wall 766 of body 754 includes an exterior
wall 766-1, which is a contiguous portion of exterior perimeter wall 766. Exterior
wall 766-1 has a chip mounting surface 766-2 that defines a plane, and has a fluid
opening 766-3 adjacent to chip mounting surface 766-2 that passes through the thickness
of exterior wall 766-1. Ejection chip 118 is mounted to chip mounting surface 766-2
and is in fluid communication with fluid opening 766-3 of exterior wall 766-1. Thus,
ejection chip 118 and its associated ejection nozzles are oriented such that the fluid
ejection direction 120-1 is substantially orthogonal to the plane of chip mounting
surface 766-2. Base wall 764 is oriented along a plane that is substantially orthogonal
to the plane of chip mounting surface 766-2 of exterior wall 766-1.
[0202] Referring to FIGs. 66, 68, and 71, body 754 of housing 752 also includes a chamber
768 located within a boundary defined by exterior perimeter wall 766. Chamber 768
forms a portion of fluid reservoir 762, and is configured to define an interior space,
and in particular, includes base wall 764 and has an interior perimetrical wall 770
configured to have a rounded perimeter so as to promote fluid flow in chamber 768.
Referring also to FIG. 67, interior perimetrical wall 770 of chamber 768 has a height
extent bounded by a proximal end 770-1 and a distal end 770-2. Proximal end 770-1
is contiguous with, and may form a transition radius with, base wall 764. Such an
edge radius may help in mixing effectiveness by reducing the number of sharp corners.
Distal end 770-2 has a perimetrical end surface 770-3 to define a lateral opening
of chamber 768. Perimetrical end surface 770-3 may be flat, or may include a plurality
of perimetrical ribs, or undulations, to provide an effective sealing surface for
engagement with diaphragm 758. Thus, in combination, chamber 768 and diaphragm 758
cooperate to define fluid reservoir 762 having a variable volume. The height extent
of interior perimetrical wall 770 of chamber 768 is substantially orthogonal to base
wall 764, and is substantially parallel to the corresponding extent of exterior perimeter
wall 766.
[0203] Referring to FIGs. 66, 69 and 70, stir bar 760 resides in the variable volume of
fluid reservoir 762. More particularly, in the orientation shown, stir bar 760 is
located in chamber 768, and is located within a boundary defined by the interior perimetrical
wall 770 of chamber 768. Stir bar 760 has a rotational axis 772 and a plurality of
paddles 760-1, 760-2, 760-3, 760-4 that radially extend away from rotational axis
772. The actual number of paddles of stir bar 760 may be two or more, and preferably
three or four, but more preferably four, with each adjacent pair of paddles having
the same angular spacing around the rotational axis 772.
[0204] Stir bar 760 has a magnet (not shown), e.g., a permanent magnet, configured for interaction
with an external magnetic field generator 164 (see FIG. 1) to drive stir bar 760 to
rotate around the rotational axis 772, using the drive principles described above.
In the present embodiment, stir bar 760 is free-floating with chamber 768, and will
be attracted into contact with base wall 764 by the application of the electromagnetic
filed generated by external magnetic field generator 164. Stir bar 760 primarily causes
rotation flow of the fluid about a central region associated with the rotational axis
772 of stir bar 760, with some axial flow with a central return path as in a partial
toroidal flow pattern.
[0205] As best shown in FIGs. 66-71, chamber 768 has an inlet fluid port 776 and an outlet
fluid port 778, each of which is formed in a portion of interior perimetrical wall
770, with inlet fluid port 776 being separated a distance from outlet fluid port 778
along a portion of interior perimetrical wall 770. In particular, interior perimetrical
wall 770 includes a divider wall 770-4 (see FIGs. 66 and 67) located between inlet
fluid port 776 and outlet fluid port 778 of the chamber 768. In the present embodiment,
the structure of inlet fluid port 776 and outlet fluid port 778 of chamber 768 is
symmetrical with respect to chamber 768, and with respect to channel mid-point 782.
[0206] The terms "inlet" and "outlet" are terms of convenience that are used in distinguishing
between the multiple ports of the present embodiment, and are correlated with a particular
rotational direction of stir bar 760. However, it is to be understood that it is the
rotational direction of stir bar 760 that dictates whether a particular port functions
as an inlet port or an outlet port, and it is within the scope of this invention to
reverse the rotational direction of stir bar 760, and thus reverse the roles of the
respective ports within chamber 768.
[0207] As best shown in FIGs. 66 and 69-71, body 754 of housing 752 includes a fluid channel
780 interposed between a portion (e.g., divider wall 770-4) of interior perimetrical
wall 770 of chamber 768 and exterior wall 766-1 of exterior perimeter wall 766 that
carries ejection chip 118. Fluid channel 780 has a channel inlet 780-1 and a channel
outlet 780-2. Fluid channel 780 dimensions, e.g., height, width, and shape, are selected
to facilitate a desired combination of fluid flow and fluid velocity for facilitating
intra-channel stirring. Fluid channel 780 is in fluid communication with each of inlet
fluid port 776 of chamber 768, outlet fluid port 778 of chamber 768, and fluid opening
766-3 of exterior wall 766-1 that mounts ejection chip 118.
[0208] Fluid channel 780 defines a passage 780-3, represented by a dashed arrowed line in
FIG. 66, which extends between channel inlet 780-1 and channel outlet 780-2. Fluid
channel 780 has an interior wall 780-4 that is positioned between channel inlet 780-1
and channel outlet 780-2, with fluid channel 780 being symmetrical about a channel
mid-point 782, and with interior wall 780-4 positioned to face fluid opening 766-3
of exterior wall 766-1 and ejection chip 118. Likewise, the structure of channel inlet
780-1 and channel outlet 780-2 of fluid channel 780 is symmetrical with respect to
the channel mid-point 782. Passage 780-3 is in fluid communication with fluid opening
766-3 in the exterior wall 766-1.
[0209] Referring also to FIGs. 67 and 68, channel inlet 780-1 of fluid channel 780 is in
fluid communication with inlet fluid port 776 of chamber 768 via an inlet transition
passage 784. Inlet transition passage 784 is oriented to extend from inlet fluid port
776 of the chamber 768 and into the channel inlet 780-1 of fluid channel 780. Inlet
transition passage 784 has a plurality of surfaces 788, 789, 790, 792, 794 that converge
in a direction 786 (see FIGs. 66, 67, and 70) from the chamber 768 toward fluid opening
766-3 in the exterior wall 766-1, such that the cross-sectional area of inlet transition
passage 784 diminishes in a direction toward fluid channel 780.
[0210] Referring to FIGs. 66-71, the plurality of surfaces 788, 789, 790, 792, 794 of the
inlet transition passage 784 includes a ramp floor 788, an inner wall 789, a tapered
ceiling 790, an angled ceiling portion 792, and a beveled side wall 794. The ramp
floor 788 is located between inner wall 789 and beveled side wall 794, and is located
to extend from base wall 764 at inlet fluid port 776 of the chamber 768 to the channel
inlet 780-1 of fluid channel 780. Each of the tapered ceiling 790 and the beveled
side wall 794 is located to extend from the interior perimetrical wall at inlet fluid
port 776 of the chamber 768 and into fluid channel 780 to an interior surface 795
of the exterior wall 766-1. The angled ceiling portion 792 transitions from the tapered
ceiling 790 to the beveled side wall 794.
[0211] Referring also to FIG. 66, in the present embodiment, ramp floor 788 has a first
transition ramp portion 788-1 and a second transition ramp portion 788-2. As best
shown in FIG. 71, the second transition ramp portion 788-2 is located closer to channel
inlet 780-1 of fluid channel 780 than the first transition ramp portion 788-1. The
first transition ramp portion 788-1 has a first slope relative to base wall 764 and
the second transition ramp portion 788-2 has a second slope relative to base wall
764. The second slope of the second transition ramp portion 788-2 is steeper than
the first slope of the first transition ramp portion 788-1.
[0212] Referring to FIGs. 66 and 67, channel outlet 780-2 of fluid channel 780 is in fluid
communication with outlet fluid port 778 of the chamber 768 via an outlet transition
passage 796. Outlet transition passage 796 is oriented to extend from outlet fluid
port 778 of the chamber 768 and into the channel outlet 780-2 of fluid channel 780.
Outlet transition passage 796 has a plurality of surfaces 798, 799, 800, 802, 804
that diverge in a direction 786-1 away from fluid opening 766-3 in the exterior wall
766-1 and toward chamber 768. Stated differently, the plurality of surfaces 798, 799,
800, 802, 804 of outlet transition passage 796 converge in a direction toward fluid
opening 766-3 in the exterior wall 766-1 and away from chamber 768, such that the
cross-sectional area of outlet transition passage 796 diminishes in a direction toward
fluid channel 780.
[0213] In the present embodiment, outlet transition passage 796 is constructed identical
to the inlet transition passage 784. At chamber 768, outlet transition passage 796
is separated from inlet transition passage 784 by divider wall 770-4. Also, in the
present embodiment, inlet transition passage 784 and the outlet transition passage
796 are symmetrical with respect to the chamber 768, and are symmetrical with respect
to channel mid-point 782. The terms "inlet" transition passage and "outlet" transition
passage are terms of convenience that are used in distinguishing between the two transition
passages of the present embodiment, and are correlated with a particular rotational
direction of stir bar 760 as to performing one of an inlet or an outlet function.
However, it is to be understood that it is the rotational direction of stir bar 760
that dictates whether a particular transition passage functions as an inlet transition
passage or an outlet transition passage, and it is within the scope of this invention
to reverse the rotational direction of stir bar 760, and thus reverse the roles of
the respective transition passages.
[0214] The plurality of surfaces 794, 799, 800, 802, 804 of outlet transition passage 796
includes a ramp floor 798, an inner wall 799, a tapered ceiling 800, an angled ceiling
portion 802, and a beveled side wall 804. The ramp floor 798 is located between inner
wall 799 and beveled side wall 804, and is located to extend from the base wall 764
at outlet fluid port 778 of the chamber 768 to the channel outlet 780-2 of fluid channel
780. Each of the tapered ceiling 800 and the beveled side wall 804 is located to extend
from the interior perimetrical wall at outlet fluid port 778 of the chamber 768 and
into fluid channel 780 to interior surface 795 of exterior wall 766-1. Angled ceiling
portion 802 transitions from tapered ceiling 800 to beveled side wall 804.
[0215] In the present embodiment, ramp floor 798 has a first transition ramp portion 798-1
and a second transition ramp portion 798-2. The second transition ramp portion 798-2
is located closer to channel outlet 780-2 of fluid channel 780 than the first transition
ramp portion 798-1. The first transition ramp portion 798-1 has a first slope relative
to base wall 764 and the second transition ramp portion 788-2 has a second slope relative
to the base wall 764. The second slope of the second transition ramp portion 798-2
is steeper than the first slope of the first transition ramp portion 798-1.
[0216] Referring to FIGs. 1-5, housing 112 includes a body 122, a lid 124, and an end cap
126. Referring to FIGs. 72 and 74, body 122 includes a fill hole 122-1 and a fill
plug 128 (e.g., ball). In the present embodiment, fill plug 128 may be in the form
of a stainless steel ball bearing. Referring to FIGs. 72-76 in relation to FIG. 1,
contained within housing 112 is a diaphragm 130 and a plurality of stir bars 132,
135. In the present embodiment, there are two stir bars that are individually identified
as stir bar 132 and stir bar 135. Each of the housing 112 components and the plurality
of stir bars 132, 135 may be made of plastic, using a molding process. Diaphragm 130
is made of rubber, using a molding process.
[0217] In general, a fluid (not shown) is loaded through a fill hole 122-1 in body 122 (see
FIGs. 72-74) into a sealed region, i.e., a fluid reservoir 136, between body 122 and
diaphragm 130. Back pressure in fluid reservoir 136 is set and then maintained by
inserting, e.g., pressing, fill plug 128 into fill hole 122-1 to prevent air from
leaking into fluid reservoir 136 or fluid from leaking out of fluid reservoir 136.
Referring again to FIGs. 1-5, end cap 126 is then placed onto an end of the body 122/lid
124 combination, opposite to ejection chip 118. The plurality of stir bars 132, 135
reside in the sealed fluid reservoir 136 between body 122 and diaphragm 130 that contains
the fluid. An internal fluid flow may be generated within fluid reservoir 136 by rotating
each of stir bar 132 and stir bar 135, so as to provide fluid mixing and redistribution
of particulate in the fluid within the sealed region of fluid reservoir 136. In the
present embodiment, as will be discussed in more detail below, the rotational direction
of stir bar 135 is opposite to the rotational direction of stir bar 132.
[0218] Referring to FIGs. 72-76, body 122 of housing 112 has a base wall 138 and an exterior
perimeter wall 140 contiguous with base wall 138. Exterior perimeter wall 140 is oriented
to extend from base wall 138 in a direction that is substantially orthogonal to base
wall 138. Referring again to FIGs. 1-5, lid 124 is configured to engage exterior perimeter
wall 140. Thus, exterior perimeter wall 140 is interposed between base wall 138 and
lid 124, with lid 124 being attached to the open free end of exterior perimeter wall
140 by weld, adhesive, or other fastening mechanism, such as a snap fit or threaded
union. Attachment of lid 124 to body 122 occurs after the insertion of the plurality
of stir bars 132, 135 (see FIG. 74) in body 122 and after the installation of diaphragm
130 (see FIGs. 72-74) on body 122.
[0219] Referring to FIGs. 72-76, exterior perimeter wall 140 of body 122 includes an exterior
wall 140-1, which is a contiguous portion of exterior perimeter wall 140. As best
shown in FIG. 75, exterior wall 140-1 has a chip mounting surface 140-2 that defines
a plane 142 (see also FIG. 72), and has a fluid opening 140-3 adjacent to chip mounting
surface 140-2 that passes through the thickness of exterior wall 140-1. Ejection chip
118 is mounted, e.g., by an adhesive, to chip mounting surface 140-2 and is in fluid
communication with fluid opening 140-3 (see FIG. 74) of exterior wall 140-1. Thus,
referring to FIGs. 1, 72 and 73, the planar extent of ejection chip 118 is oriented
along plane 142, with the plurality of ejection nozzles 120 oriented such that the
fluid ejection direction 120-1 is substantially orthogonal to plane 142. Base wall
138 is oriented along a plane 146 (see FIGs. 72 and 74) that is substantially orthogonal
to plane 142 of exterior wall 140-1.
[0220] Referring to FIGs. 74-77, body 122 of housing 112 also includes a chamber 148 located
within a boundary defined by exterior perimeter wall 140. Chamber 148 forms a portion
of fluid reservoir 136, and is configured to define an interior space, and in particular,
includes base wall 138 and has an interior perimetrical wall 150 configured to have
rounded corners, so as to promote fluid flow in chamber 148. Each of the plurality
of stir bars 132, 135 is rotatable, and moveable laterally and longitudinally along
base wall 138, within the confining limits defined by interior perimetrical wall 150
of fluid reservoir 136. In the present embodiment, stir bar 132 of the plurality of
stir bars 132, 135 is located closer to inlet fluid port 152 and an outlet fluid port
154 than is stir bar 135. Stated differently, as illustrated in FIG. 76, for example,
stir bar 132 is interposed between fluid ports 152, 154 and stir bar 135, and in turn,
as illustrated in FIG. 75, stir bar 132 is interposed between fluid opening 140-3
and stir bar 135.
[0221] Interior perimetrical wall 150 of chamber 148 has an extent bounded by a proximal
end 150-1 and a distal end 150-2. Proximal end 150-1 is contiguous with, and may form
a transition radius with, base wall 138. Such an edge radius may help in mixing effectiveness
by reducing the number of sharp corners. Distal end 150-2 is configured to define
a perimetrical end surface 150-3 at an open end 148-2 of chamber 148. Perimetrical
end surface 150-3 may include a plurality of perimetrical ribs, or undulations, to
provide an effective sealing surface for engagement with diaphragm 130 (see FIGs.
72-77). The extent of interior perimetrical wall 150 of chamber 148 is substantially
orthogonal to base wall 138, and is substantially parallel to the corresponding extent
of exterior perimeter wall 140 (see FIGs. 75 and 76).
[0222] As best shown in FIG. 76, chamber 148 has an inlet fluid port 152 and an outlet fluid
port 154, each of which is formed in a portion of interior perimetrical wall 150.
The terms "inlet" and "outlet" are terms of convenience that are used in distinguishing
between the multiple ports of the present embodiment, and are correlated with a particular
rotational direction of the stir bar of the plurality of stir bars 132, 135 that is
located closer to inlet fluid port 152 and an outlet fluid port 154, which as illustrated
in FIG. 76, for example, is stir bar 132. In other words, it is the rotational direction
of the closer stir bar that dictates whether a particular port functions as an inlet
port or an outlet port, and it is within the scope of this invention to reverse the
rotational direction of the plurality of stir bars 132, 135, and thus reverse the
roles of the respective ports within chamber 148.
[0223] As shown in FIG. 76, inlet fluid port 152 is separated a distance from outlet fluid
port 154 along a portion of interior perimetrical wall 150. Referring also to FIG.
74, body 122 of housing 112 includes a fluid channel 156 interposed between the portion
of interior perimetrical wall 150 of chamber 148 and exterior wall 140-1 of exterior
perimeter wall 140 that carries ejection chip 118.
[0224] Fluid channel 156 is configured to minimize particulate settling in a region of ejection
chip 118. Fluid channel 156 is sized, e.g., using empirical data, to provide a desired
flow rate while also maintaining an acceptable fluid velocity for fluid mixing through
fluid channel 156. In the present embodiment, fluid channel 156 is configured as a
U-shaped elongated passage. Fluid channel 156 dimensions, e.g., height and width,
and shape are selected to provide a desired combination of fluid flow and fluid velocity
for facilitating intra-channel stirring. Fluid channel 156 is configured to connect
inlet fluid port 152 of chamber 148 in fluid communication with outlet fluid port
154 of chamber 148, and also connects fluid opening 140-3 (see FIG. 75) of exterior
wall 140-1 of exterior perimeter wall 140 in fluid communication with both inlet fluid
port 152 and outlet fluid port 154 (see FIG. 76) of chamber 148.
[0225] Referring again to FIGs. 1, 72, and 73, diaphragm 130 is positioned between lid 124
and perimetrical end surface 150-3 of interior perimetrical wall 150 of chamber 148.
The attachment of lid 124 to body 122 compresses a perimeter of diaphragm 130 thereby
creating a continuous seal between diaphragm 130 and body 122. More particularly,
diaphragm 130 is configured for sealing engagement with perimetrical end surface 150-3
of interior perimetrical wall 150 of chamber 148 in forming fluid reservoir 136. Thus,
in combination, chamber 148 and diaphragm 130 cooperate to define fluid reservoir
136 having a variable volume.
[0226] Referring particularly to FIGs. 1 and 72, an exterior surface of diaphragm 130 is
vented to the atmosphere through a vent hole 124-1 located in lid 124 so that a controlled
negative pressure can be maintained in fluid reservoir 136. Diaphragm 130 is made
of rubber, and includes a dome portion 130-1 configured to progressively collapse
toward base wall 138 as fluid is depleted from microfluidic dispensing device 110,
so as to maintain a desired negative pressure in chamber 148, and thus changing the
effective volume of the variable volume of fluid reservoir 136, also referred to herein
as a bulk region.
[0227] Referring to FIGs. 72-77, stir bar 132 moveably resides in, and is confined within,
the variable volume of fluid reservoir 136 and chamber 148, and is located within
a boundary defined by the interior perimetrical wall 150 of chamber 148.
[0228] Referring also to FIG. 78, stir bar 132 has a rotational axis 160 and a plurality
of paddles 132-1, 132-2, 132-3, 132-4 that radially extend away from rotational axis
160 to rotate about rotational axis 160 in a rotational direction 160-1 to define
a rotational area 160-2 of stir bar 132. While rotational area 160-2 is depicted as
being circular as to a single revolution of stir bar 132 about rotational axis 160,
it is to be understood that within a single revolution of stir bar 132 it is possible
that the location of rotational axis 160 relative to fluid reservoir 136, base wall
138, and chamber 148 may shift radially, thus resulting in a non-circular, e.g., oval,
shape for rotational area 160-2 of stir bar 132. As depicted in FIG. 77, stir bar
132 has a magnet 162, e.g., a permanent bar magnet having opposed poles, i.e., a North
pole and a South pole.
[0229] Likewise, referring again to FIG. 78, stir bar 135 has a rotational axis 165 and
a plurality of paddles 135-1, 135-2, 135-3, 135-4 that radially extend away from rotational
axis 165 to rotate about rotational axis 165 in a rotational direction 165-1 to define
a rotational area 165-2 of stir bar 135. While rotational area 165-2 is depicted as
being circular as to a single revolution of stir bar 135 about rotational axis 165,
it is to be understood that within a single revolution of stir bar 135 it is possible
that the location of rotational axis 165 relative to fluid reservoir 136, base wall
138, and chamber 148 may shift radially, thus resulting in a non-circular, e.g., oval,
shape for rotational area 165-2 of stir bar 135. As depicted in FIG. 77, stir bar
135 has a magnet 167, e.g., a permanent bar magnet having opposed poles, i.e., a North
pole and a South pole.
[0230] In the present example, with reference to FIGs. 74-78, the plurality of paddles 132-1,
132-2, 132-3, 132-4 of stir bar 132 are in-mesh with the plurality of paddles 135-1,
135-2, 135-3, 135-4 of stir bar 135, and as such, rotational direction 160-1 of stir
bar 132 is opposite to the rotational direction 165-1 of stir bar 135. Also, in the
present embodiment, an in-mesh timing sequence of the plurality of paddles 132-1,
132-2, 132-3, 132-4 of stir bar 132 with the plurality of paddles 135-1, 135-2, 135-3,
135-4 is such that the like poles of magnet 162 of stir bar 132 and magnet 167 of
stir bar 135 repel to aid in opposed rotational directions of stir bar 132 and stir
bar 135. As depicted in FIG. 78, the in-mesh relationship of the plurality of paddles
132-1, 132-2, 132-3, 132-4 of stir bar 132 with the plurality of paddles 135-1, 135-2,
135-3, 135-4 of stir bar 135 results in an overlap of the rotational area 160-2 of
stir bar 132 with the rotational area 165-2 of stir bar 135.
[0231] In operation, each of magnet 162 of stir bar 132 and magnet 167 of stir bar 135 interact
with an external magnetic field generator 168 (see FIG. 1) to cause the plurality
of stir bars 132, 135 to rotate around their respective rotational axes 160, 165.
The principle of operation of the plurality of stir bars 132, 135 is that as magnets
162, 167 are aligned to a strong enough external magnetic field generated by external
magnetic field generator 168, then rotating the external magnetic field generated
by external magnetic field generator 168 in a controlled manner will rotate the plurality
of stir bars 132, 135 in a chaotic, somewhat erratic, manner due to the interaction
of the magnetic fields of magnets 162, 167, wherein like poles repel and unlike poles
attract, and/or due to impact of stir bars 132, 135 with each other or with interior
perimetrical wall 150 of body 122. The external magnetic field generated by external
magnetic field generator 168 may be electronically rotated, akin to operation of a
stepper motor, or may be rotated via a rotating shaft. Thus, the plurality of stir
bars 132, 135 are effective to provide fluid mixing in fluid reservoir 136 by the
rotation of stir bar 132 around rotational axis 160 and by the rotation of stir bar
135 around rotational axis 165.
[0232] While in the present embodiment, each of stir bar 132 and 135 has a respective magnet,
162, 167, those skilled in the art will recognize that due to the in-mesh relationship
of the plurality of paddles 132-1, 132-2, 132-3, 132-4 of stir bar 132 with the plurality
of paddles 135-1, 135-2, 135-3, 135-4 of stir bar 135, it is possible to include a
magnet in only one of stir bars 132, 135. For example, assume that stir bar 132 includes
magnet 162, but stir bar 135 does not. As such, stir bar 132 will interact with the
rotating external magnetic field generated by external magnetic field generator 168,
but stir bar 135 will not. However, due to the overlap of the rotational area 160-2
of stir bar 132 with the rotational area 165-2 of stir bar 135 that results in the
in-mesh relationship, stir bar 135 will be driven to rotate by the rotation of stir
bar 132.
[0233] Fluid mixing in the bulk region relies on a flow velocity caused by rotation of the
plurality of stir bars 132, 135 to create a shear stress at the settled boundary layer
of the particulate. When the shear stress is greater than the critical shear stress
(empirically determined) to start particle movement, remixing occurs because the settled
particles are now distributed in the moving fluid. The shear stress is dependent on
both the fluid parameters such as: viscosity, particle size, and density; and mechanical
design factors such as: container shape, stir bar geometry, fluid thickness between
moving and stationary surfaces, and rotational speed.
[0234] A fluid flow is generated by rotating the plurality of stir bars 132, 135 in a fluid
region, e.g., fluid reservoir 136, and fluid channel 156 associated with ejection
chip 118, so as to ensure that mixed bulk fluid is presented to ejection chip 118
for nozzle ejection and to move fluid adjacent to ejection chip 118 to the bulk region
of fluid reservoir 136 to ensure that the channel fluid flowing through fluid channel
156 mixes with the bulk fluid of fluid reservoir 136, so as to produce a more uniform
mixture. Although this flow is primarily distribution in nature, some mixing will
occur if the flow velocity is sufficient to create a shear stress above the critical
value.
[0235] The combination of the rotation of stir bar 132 and the counter rotation of stir
bar 135 results in a rotational flow of the fluid about a central region associated
with each of rotational axis 160 of stir bar 132 and rotational axis 165 of stir bar
135. In the present embodiment, rotational axis 160 of stir bar 132 and rotational
axis 165 of stir bar 135 are moveable within the confinement range defined by fluid
reservoir 136, and within chamber 148.
[0236] Referring to FIGs. 74-78, each paddle of the plurality of paddles 132-1, 132-2, 132-3,
132-4 of stir bar 132 has a respective free end tip 132-5. Referring to FIG. 74, so
as to reduce rotational drag, each paddle may include upper and lower symmetrical
pairs of chamfered surfaces, forming leading beveled surfaces 132-6 and trailing beveled
surfaces 132-7 relative to a rotational direction 160-1 of stir bar 132. It is also
contemplated that each of the plurality of paddles 132-1, 132-2, 132-3, 132-4 of stir
bar 132 may have a pill or cylindrical shape. In the present embodiment, stir bar
132 has two pairs of diametrically opposed paddles, wherein a first paddle of the
diametrically opposed paddles has a first free end tip 132-5 and a second paddle of
the diametrically opposed paddles has a second free end tip 132-5.
[0237] Likewise, referring to FIGs. 74-78, each paddle of the plurality of paddles 135-1,
135-2, 135-3, 135-4 of stir bar 135 has a respective free end tip 135-5. Referring
to FIG. 74, so as to reduce rotational drag, each paddle may include upper and lower
symmetrical pairs of chamfered surfaces, forming leading beveled surfaces 135-6 and
trailing beveled surfaces 135-7 relative to a rotational direction 165-1 of stir bar
135. It is also contemplated that each of the plurality of paddles 135-1, 135-2, 135-3,
135-4 of stir bar 135 may have a pill or cylindrical shape. In the present embodiment,
stir bar 135 has two pairs of diametrically opposed paddles, wherein a first paddle
of the diametrically opposed paddles has a first free end tip 135-5 and a second paddle
of the diametrically opposed paddles has a second free end tip 135-5.
[0238] In the present embodiment, for each of the stir bars 132, 135, the four paddles forming
the two pairs of diametrically opposed paddles are equally spaced at 90 degree increments
around the respective rotational axis of rotational axes 160, 165. However, the actual
number of paddles may be two or more, and preferably three or four, but more preferably
four, with each adjacent pair of paddles having the same angular spacing around the
respective rotational axis of rotational axes 160, 165. For example, a stir bar configuration
having three paddles may have a paddle spacing of 120 degrees, having four paddles
may have a paddle spacing of 90 degrees, etc.
[0239] Referring to FIGs. 72-76, the plurality of stir bars 132, 135 are located for movement
within the variable volume of fluid reservoir 136 (see FIG. 72 and 74), and more particularly,
within the boundary defined by interior perimetrical wall 150 of chamber 148 (see
also FIGs. 75-77).
[0240] As such, in the present embodiment, the plurality of stir bars 132, 135 are confined
within fluid reservoir 136 by the confining surfaces provided by fluid reservoir 136,
e.g., by chamber 148 and diaphragm 130. The extent to which the respective stir bars
132, 135 are movable within fluid reservoir 136 is determined by the radial tolerances
provided between each of the stir bars 132, 135 and the interior perimetrical wall
150 of chamber 148 in the radial (lateral/longitudinal) direction, and by the axial
tolerances between each of the stir bars 132, 135 and the axial limit provided by
the combination of base wall 138 of chamber 148 and diaphragm 130.
[0241] Thus, referring to FIGs. 73-76, the rotational axes 160, 165 of the plurality of
stir bars 132, 135 are free to move radially and axially, e.g., longitudinally, laterally,
and/or vertically, within fluid reservoir 136 to the extent permitted by the confining
surfaces, e.g., interior surfaces of chamber 148 and diaphragm 130, of fluid reservoir
136. Such confining surfaces also limit the canting of the rotational axes 160, 165
of the plurality of stir bars 132, 135 to be within a predefined angular range, e.g.,
perpendicular, plus or minus 45 degrees, relative to plane 146 of base wall 138 of
chamber 148 and/or to the fluid ejection direction 120-1 (see also FIG. 73). Stated
differently, the rotational axes 160, 165 of the plurality of stir bars 132, 135 are
moveable radially and axially within fluid reservoir 136, and may be canted in an
angular range of perpendicular, plus or minus 45 degrees, relative to plane 146 of
base wall 138 of chamber 148 and/or to the fluid ejection direction 120-1.
[0242] In the present embodiment, referring to FIGs. 74-77, the plurality of stir bars 132,
135 are moveably confined within fluid reservoir 136, and the confining surfaces of
fluid reservoir 136 maintain an orientation of stir bar 132 such that the free end
tip 132-5 of a respective paddle of the plurality of paddles 132-1, 132-2, 132-3,
132-4 periodically and intermittently face inlet and outlet fluid ports 152, 154;
fluid channel 156; fluid opening 140-3; and ejection chip 118, as stir bar 132 is
rotated about rotational axis 160, and permits movement of the plurality of stir bars
132, 135 toward or away from inlet and outlet fluid ports 152, 154; fluid channel
156; fluid opening 140-3; and ejection chip 118.
[0243] In accordance with an aspect of the present embodiment, to effect movement of the
location of the plurality of stir bars 132, 135 within fluid reservoir 136, first,
external magnetic field generator 168 (see FIG. 1) is energized to interact with each
of magnet 162 (see FIG. 77) of stir bar 132 and magnet 167 of stir bar 135. If the
magnetic field generated by external magnetic field generator 168 is rotating, then
the plurality of stir bars 132, 135 will tend to rotate with the magnetic field. Next,
housing 112 of microfluidic dispensing device 110 may be moved relative to external
magnetic field generator 168, or vice versa.
[0244] In other words, magnets 162, 167 of the plurality of stir bars 132, 135 are attracted
to the magnetic field generated by external magnetic field generator 168, such that
rotational axis 160 and rotational area 160-2 of stir bar 132, and rotational axis
165 and rotational area 165-2 of stir bar 135, will be relocated within fluid reservoir
136 and chamber 148 with a change of location of external magnetic field generator
168 relative to the location of housing 112 of microfluidic dispensing device 110.
The attraction of the plurality of stir bars 132, 135 to the magnetic field generated
by external magnetic field generator 168 can cause rotational axis 160 of stir bar
132 and rotational axis 165 of stir bar 135 to attempt to occupy the same space, which
is not possible, thus resulting in erratic radial movement of stir bar 132 relative
to stir bar 135 that causes stir bars 132, 135 to sweep a larger area. Also, such
an attempt to occupy the same space may result in an intermittent radial impact of
stir bar 132 with stir bar 135, resulting in a vibratory effect that may be beneficial
in loosening settled particulate in fluid reservoir 136.
[0245] Referring to FIGs. 79-84, there is shown an alternative body 200, which may be substituted
for the body 122 depicted in FIGs. 1-5 and 72-77. Body 200 is identical in all respects
to body 122 except for the inclusion of a separation wall 202. As such, the description
set forth above as to features common to body 122 and to body 200 also will apply
to body 200, and thus, for brevity, the full description of such features common to
body 122 and to body 200 will not be repeated here although such common features will
be identified in FIGs. 79-84. In particular, the difference between body 200 and body
122 is that of the inclusion of separation wall 202 in body 200, which will be described
in detail below.
[0246] Referring to FIG. 84, separation wall 202 is positioned in fluid reservoir 136 between
base wall 138 and diaphragm 130 to divide fluid reservoir 136, and in turn chamber
148, into a first region 204 and a second region 206 (see also FIG. 83). Referring
also to FIGs. 79-82, separation wall 202 has at least one transverse opening 208,
and in the present embodiment, includes a plurality of transverse openings 208, which
are individually identified as transverse opening 208-1, transverse opening 208-2,
transverse opening 208-3, transverse opening 208-4 and transverse opening 208-5. Each
of the plurality of transverse openings 208 connects the first region 204 in fluid
communication with the second region 206. Referring also to FIG. 83, separation wall
202 is interposed between the stir bar 132 and the stir bar 135 of the plurality of
stir bars 132, 135, such that stir bar 132 is located in its entirety in the first
region 204 and stir bar 135 is located in its entirety in the second region 206.
[0247] As best shown in FIGs. 79-81, with reference to FIG. 84, separation wall 202 has
a profile shape selected to facilitate a collapse of diaphragm 130 toward base wall
138 as fluid is depleted from fluid reservoir 136 and chamber 148. In addition, the
shape, e.g., height, of separation wall 202 is selected to prevent contact of diaphragm
130 with either of the plurality of stir bars 132, 135. In the present embodiment,
separation wall 202 may include two or more spaced posts 211. In the present example,
referring also to FIG. 82, there are four posts that are individually identified as
post 211-1, post 211-2, post 211-3, and post 211-4. Each of the posts 211 extend from
base wall 138 in a direction substantially perpendicular to base wall 138 to a respective
free end tip 212-1, free end tip 212-2, free end tip 212-3, and free end tip 212-4.
In other words, in the present embodiment, each of the posts 211 of separation wall
202 extends in a cantilever manner from base wall 138.
[0248] Thus, referring to FIGs. 83 and 84, at least a portion of separation wall 202 is
taller than a height of each of the stir bars 132, 135. In the present embodiment,
referring to FIGs. 79-82, in the present embodiment, the outer posts 211-1, 211-4
of posts 211 are the same length as measured from base wall 138, the central posts
211-2, 211-3 of posts 211 are the same length as measured from base wall 138, and
the central posts 211-2, 211-3 are longer than the outer posts 211-1, 211-4. In the
present embodiment, an extent of each of the central posts 211-2, 211-3 of posts 211
from base wall 138 to its respective free end tip is longer than a height of each
of the stir bars 132, 135 (see FIGs. 81, 83 and 84).
[0249] As identified in FIGs. 79, 80, and 82, a respective transverse opening of the plurality
of transverse openings 208 is present between any two adjacent posts of the plurality
of spaced posts 211 to facilitate fluid communication between the first region 204
and the second region 206. Referring to FIG. 82, for example, in the present embodiment
the transverse opening 208-1 is located between interior perimetrical wall 150 and
post 211-1; transverse opening 208-2 is located between post 211-1 and post 211-2;
transverse opening 208-3 is located between post 211-2 and post 211-3; transverse
opening 208-4 is located between post 211-3 and post 211-4; and transverse opening
208-5 is located between post 211-4 and interior perimetrical wall 150.
[0250] As depicted in FIG. 85, rotational area 160-2 of stir bar 132 is located in its entirety
in first region 204. Likewise, rotational area 165-2 of stir bar 135 is located in
its entirety in second region 206. Thus, in contrast to the non-separated embodiment
depicted in FIGs. 77-78, body 200 having separation wall 202 separates the first rotational
area 160-2 of stir bar 132 from the second rotational area 165-2 of the stir bar 135.
The separation wall 202 prevents first rotational area 160-2 of stir bar 132 from
overlapping, i.e., intersecting, the second rotational area 165-2 of stir bar 135.
In turn, the plurality of paddles 132-1, 132-2, 132-3, 132-4 of stir bar 132 are prevented
from being in-mesh with the plurality of paddles 135-1, 135-2, 135-3, 135-4 of stir
bar 135. As such, in the embodiment of FIGs. 79-85, the respective rotational direction
of each of stir bar 132 and stir bar 135 may be in opposite rotational directions,
may be in the same rotational direction, or may periodically change between the same
rotational direction and opposite rotational directions.
[0251] In general, a fluid (not shown) is loaded through a fill hole 122-1 in body 122 (see
FIGs. 72 and 86-88) into a sealed region, i.e., a fluid reservoir 136, between body
122 and diaphragm 130. Back pressure in fluid reservoir 136 is set and then maintained
by inserting, e.g., pressing, fill plug 128 into fill hole 122-1 to prevent air from
leaking into fluid reservoir 136 or fluid from leaking out of fluid reservoir 136.
Referring again to FIGs. 1-5, end cap 126 is then placed onto an end of the body 122/lid
124 combination, opposite to ejection chip 118. Stir bar 132 resides in the sealed
fluid reservoir 136 between body 122 and diaphragm 130 that contains the fluid. An
internal fluid flow may be generated within fluid reservoir 136 by rotating stir bar
132 so as to provide fluid mixing and redistribution of particulate in the fluid within
the sealed region of fluid reservoir 136.
[0252] Referring to FIGs. 72 and 86-89, body 122 of housing 112 has a base wall 138 and
an exterior perimeter wall 140 contiguous with base wall 138. Exterior perimeter wall
140 is oriented to extend from base wall 138 in a direction that is substantially
orthogonal to base wall 138. Referring again to FIGs. 1-5, lid 124 is configured to
engage exterior perimeter wall 140. Thus, exterior perimeter wall 140 is interposed
between base wall 138 and lid 124, with lid 124 being attached to the open free end
of exterior perimeter wall 140 by weld, adhesive, or other fastening mechanism, such
as a snap fit or threaded union. Attachment of lid 124 to body 122 occurs after installation
of diaphragm 130 (see FIG. 72) and stir bar 132 (see FIG. 86) in body 122.
[0253] Referring to FIGs. 72 and 86-89, exterior perimeter wall 140 of body 122 includes
an exterior wall 140-1, which is a contiguous portion of exterior perimeter wall 140.
As best shown in FIG. 86, exterior wall 140-1 has a chip mounting surface 140-2 that
defines a plane 142 (see also FIG. 72), and has a fluid opening 140-3 adjacent to
chip mounting surface 140-2 that passes through the thickness of exterior wall 140-1.
Ejection chip 118 is mounted, e.g., by an adhesive, to chip mounting surface 140-2
and is in fluid communication with fluid opening 140-3 (see FIG. 86) of exterior wall
140-1. Thus, the planar extent of ejection chip 118 is oriented along plane 142, with
the plurality of ejection nozzles 120 oriented such that the fluid ejection direction
120-1 is substantially orthogonal to plane 142. Base wall 138 is oriented along a
plane 146 (see FIGs. 72 and 86) that is substantially orthogonal to plane 142 of exterior
wall 140-1.
[0254] Referring to FIGs. 86-89, body 122 of housing 112 also includes a chamber 148 located
within a boundary defined by exterior perimeter wall 140. Chamber 148 forms a portion
of fluid reservoir 136, and is configured to define an interior space, and in particular,
includes base wall 138 and has an interior perimetrical wall 150 configured to have
rounded corners, so as to promote fluid flow in chamber 148. Stir bar 132 is moveable
laterally and longitudinally along base wall 138 within the confining limits defined
by interior perimetrical wall 150 of fluid reservoir 136.
[0255] Interior perimetrical wall 150 of chamber 148 has an extent bounded by a proximal
end 150-1 and a distal end 150-2. Proximal end 150-1 is contiguous with, and may form
a transition radius with, base wall 138. Such an edge radius may help in mixing effectiveness
by reducing the number of sharp corners. Distal end 150-2 is configured to define
a perimetrical end surface 150-3 at an open end 148-2 of chamber 148. Perimetrical
end surface 150-3 may include a plurality of perimetrical ribs, or undulations, to
provide an effective sealing surface for engagement with diaphragm 130 (see FIG. 72).
The extent of interior perimetrical wall 150 of chamber 148 is substantially orthogonal
to base wall 138, and is substantially parallel to the corresponding extent of exterior
perimeter wall 140 (see FIG. 86).
[0256] As best shown in FIG. 87, chamber 148 has an inlet fluid port 152 and an outlet fluid
port 154, each of which is formed in a portion of interior perimetrical wall 150.
The terms "inlet" and "outlet" are terms of convenience that are used in distinguishing
between the multiple ports of the present embodiment, and are correlated with a particular
rotational direction of stir bar 132. However, it is to be understood that it is the
rotational direction of stir bar 132 that dictates whether a particular port functions
as an inlet port or an outlet port, and it is within the scope of this invention to
reverse the rotational direction of stir bar 132, and thus reverse the roles of the
respective ports within chamber 148.
[0257] Inlet fluid port 152 is separated a distance from outlet fluid port 154 along a portion
of interior perimetrical wall 150. As best shown in FIG. 89, body 122 of housing 112
includes a fluid channel 156 interposed between the portion of interior perimetrical
wall 150 of chamber 148 and exterior wall 140-1 of exterior perimeter wall 140 that
carries ejection chip 118.
[0258] Fluid channel 156 is configured to minimize particulate settling in a region of ejection
chip 118. Fluid channel 156 is sized, e.g., using empirical data, to provide a desired
flow rate while also maintaining an acceptable fluid velocity for fluid mixing through
fluid channel 156. In the present embodiment, fluid channel 156 is configured as a
U-shaped elongated passage. Fluid channel 156 dimensions, e.g., height and width,
and shape are selected to provide a desired combination of fluid flow and fluid velocity
for facilitating intra-channel stirring. Fluid channel 156 is configured to connect
inlet fluid port 152 of chamber 148 in fluid communication with outlet fluid port
154 of chamber 148, and also connects fluid opening 140-3 (see FIG. 86) of exterior
wall 140-1 of exterior perimeter wall 140 in fluid communication with both inlet fluid
port 152 and outlet fluid port 154 (see FIG. 87) of chamber 148.
[0259] Referring again to FIGs. 1, 72, and 86, diaphragm 130 is positioned between lid 124
and perimetrical end surface 150-3 of interior perimetrical wall 150 of chamber 148.
The attachment of lid 124 to body 122 compresses a perimeter of diaphragm 130 thereby
creating a continuous seal between diaphragm 130 and body 122. More particularly,
diaphragm 130 is configured for sealing engagement with perimetrical end surface 150-3
of interior perimetrical wall 150 of chamber 148 in forming fluid reservoir 136. Thus,
in combination, chamber 148 and diaphragm 130 cooperate to define fluid reservoir
136 having a variable volume.
[0260] Referring particularly to FIGs. 1 and 72, an exterior surface of diaphragm 130 is
vented to the atmosphere through a vent hole 124-1 located in lid 124 so that a controlled
negative pressure can be maintained in fluid reservoir 136. Diaphragm 130 is made
of rubber, and includes a dome portion 130-1 configured to progressively collapse
toward base wall 138 as fluid is depleted from microfluidic dispensing device 110,
so as to maintain a desired negative pressure in chamber 148, and thus changing the
effective volume of the variable volume of fluid reservoir 136, also referred to herein
as a bulk region.
[0261] Referring to FIGs. 72 and 86-89, stir bar 132 moveably resides in, and is confined
within, the variable volume of fluid reservoir 136 and chamber 148, and is located
within a boundary defined by the interior perimetrical wall 150 of chamber 148. In
the present embodiment, stir bar 132 has a rotational axis 160 and a plurality of
paddles 132-1, 132-2, 132-3, 132-4 that radially extend away from the rotational axis
160. Stir bar 132 has a magnet 162 (see FIG. 88), e.g., a permanent magnet, configured
for interaction with an external magnetic field generator 164 (see FIG. 1) to drive
stir bar 132 to rotate around the rotational axis 160. The principle of stir bar 132
operation is that as magnet 162 is aligned to a strong enough external magnetic field
generated by external magnetic field generator 164, then rotating the external magnetic
field generated by external magnetic field generator 164 in a controlled manner will
rotate stir bar 132. The external magnetic field generated by external magnetic field
generator 164 may be rotated electronically, akin to operation of a stepper motor,
or may be rotated via a rotating shaft. Thus, stir bar 132 is effective to provide
fluid mixing in fluid reservoir 136 by the rotation of stir bar 132 around the rotational
axis 160.
[0262] Fluid mixing in the bulk region relies on a flow velocity caused by rotation of stir
bar 132 to create a shear stress at the settled boundary layer of the particulate.
When the shear stress is greater than the critical shear stress (empirically determined)
to start particle movement, remixing occurs because the settled particles are now
distributed in the moving fluid. The shear stress is dependent on both the fluid parameters
such as: viscosity, particle size, and density; and mechanical design factors such
as: container shape, stir bar geometry, fluid thickness between moving and stationary
surfaces, and rotational speed.
[0263] A fluid flow is generated by rotating stir bar 132 in a fluid region, e.g., fluid
reservoir 136, and fluid channel 156 associated with ejection chip 118, so as to ensure
that mixed bulk fluid is presented to ejection chip 118 for nozzle ejection and to
move fluid adjacent to ejection chip 118 to the bulk region of fluid reservoir 136
to ensure that the channel fluid flowing through fluid channel 156 mixes with the
bulk fluid of fluid reservoir 136, so as to produce a more uniform mixture. Although
this flow is primarily distribution in nature, some mixing will occur if the flow
velocity is sufficient to create a shear stress above the critical value.
[0264] Stir bar 132 primarily causes rotation flow of the fluid about a central region associated
with the rotational axis 160 of stir bar 132, with some axial flow with a central
return path as in a partial toroidal flow pattern. Advantageously, in the present
embodiment, the rotational axis 160 of stir bar 132 is moveable within the confinement
range defined by fluid reservoir 136.
[0265] Referring to FIGs. 86-89, each paddle of the plurality of paddles 132-1, 132-2, 132-3,
132-4 of stir bar 132 has a respective free end tip 132-5. Referring to FIGs. 87-89,
so as to reduce rotational drag, each paddle may include upper and lower symmetrical
pairs of chamfered surfaces, forming leading beveled surfaces 132-6 and trailing beveled
surfaces 132-7 relative to a rotational direction 160-1 of stir bar 132. It is also
contemplated that each of the plurality of paddles 132-1, 132-2, 132-3, 132-4 of stir
bar 132 may have a pill or cylindrical shape. In the present embodiment, stir bar
132 has two pairs of diametrically opposed paddles, wherein a first paddle of the
diametrically opposed paddles has a first free end tip 132-5 and a second paddle of
the diametrically opposed paddles has a second free end tip 132-5.
[0266] In the present embodiment, the four paddles forming the two pairs of diametrically
opposed paddles are equally spaced at 90 degree increments around the rotational axis
160. However, the actual number of paddles of stir bar 132 may be two or more, and
preferably three or four, but more preferably four, with each adjacent pair of paddles
having the same angular spacing around the rotational axis 160. For example, a stir
bar 132 configuration having three paddles may have a paddle spacing of 120 degrees,
having four paddles may have a paddle spacing of 90 degrees, etc.
[0267] Referring to FIGs. 72 and 86-89, stir bar 132 is located for movement within the
variable volume of fluid reservoir 136 (see FIG. 72), and more particularly, within
the boundary defined by interior perimetrical wall 150 of chamber 148 (see FIGs. 86-89).
[0268] As such, in the present embodiment, stir bar 132 is confined within fluid reservoir
136 by the confining surfaces provided by fluid reservoir 136, e.g., by chamber 148
and diaphragm 130. The extent to which stir bar 132 is movable within fluid reservoir
136 is determined by the radial tolerances provided between stir bar 132 and interior
perimetrical wall 150 of chamber 148 in the radial (lateral/longitudinal) direction,
and by the axial tolerances between stir bar 132 and the axial limit provided by the
combination of base wall 138 of chamber 148 and diaphragm 130.
[0269] Thus, referring to FIGs. 86-89, the rotational axis 160 of stir bar 132 is free to
move radially and axially, e.g., longitudinally, laterally, and/or vertically, within
fluid reservoir 136 to the extent permitted by the confining surfaces, e.g., interior
surfaces of chamber 148 and diaphragm 130, of fluid reservoir 136. Such confining
surfaces also limit the canting of the rotational axis 160 of stir bar 132 to be within
a predefined angular range, e.g., perpendicular, plus or minus 45 degrees, relative
to plane 146 of base wall 138 of chamber 148 and/or to the fluid ejection direction
120-1. Stated differently, the rotational axis 160 of stir bar 132 is moveable radially
and axially within fluid reservoir 136, and may be canted in an angular range of perpendicular,
plus or minus 45 degrees, relative to plane 146 of base wall 138 of chamber 148 and/or
to the fluid ejection direction 120-1.
[0270] In the present embodiment, referring to FIGs. 72 and 86-89, stir bar 132 is moveably
confined within fluid reservoir 136, and the confining surfaces of fluid reservoir
136 maintain an orientation of stir bar 132 such that the free end tip 132-5 of a
respective paddle of the plurality of paddles 132-1, 132-2, 132-3, 132-4 periodically
face fluid channel 156, and in turn, intermittently face toward fluid opening 140-3
that is in fluid communication with ejection chip 118, as stir bar 132 is rotated
about the rotational axis 160, and permits movement of stir bar 132 toward or away
from inlet and outlet fluid ports 152, 154; fluid channel 156; fluid opening 140-3;
and ejection chip 118.
[0271] In accordance with the present invention, to effect movement of the location of stir
bar 132 within fluid reservoir 136, first, external magnetic field generator 164 (see
FIG. 1) is energized to interact with magnet 162 (see FIG. 87), e.g., a permanent
magnet, of stir bar 132. If the magnetic field generated by external magnetic field
generator 164 is rotating, then stir bar 132 will tend to rotate in unison with the
rotation of the magnetic field. Next, housing 112 of microfluidic dispensing device
110 is moved relative to external magnetic field generator 164, or vice versa. In
other words, magnet 162 of stir bar 132 is attracted to the magnetic field generated
by external magnetic field generator 164, such that the rotational axis 160 of stir
bar 132 will be relocated within fluid reservoir 136 with a change of location of
external magnetic field generator 164 relative to the location of housing 112 of microfluidic
dispensing device 110.
[0272] It is contemplated that the movement pattern of the rotational axis 160 of stir bar
132 may be linear, e.g., longitudinal, lateral, diagonal, X-shaped, Z-shaped, etc.,
or may be non-linear, such as curved, circular, elliptical, a figure 8 pattern, etc.
[0273] FIGs. 90-100 depict another embodiment of the invention, which in the present example
is in the form of a microfluidic dispensing device 210. Elements common to both microfluidic
dispensing device 110 and microfluidic dispensing device 210 are identified using
common element numbers, and for brevity, are not described again below in full detail.
[0274] Microfluidic dispensing device 210 generally includes a housing 212 and TAB circuit
114, with microfluidic dispensing device 210 configured to contain a supply of a fluid,
such as a particulate carrying fluid, and with TAB circuit 114 configured to facilitate
the ejection of the fluid from housing 212.
[0275] As best shown in FIGs. 90-92, housing 212 includes a body 214, a lid 216, an end
cap 218, and a fill plug 220 (e.g., ball). Contained within housing 212 is a diaphragm
222, a stir bar 224, and a guide portion 226. Each of housing 212 components, stir
bar 224, and guide portion 226 may be made of plastic, using a molding process. Diaphragm
222 is made of rubber, using a molding process. Also, in the present embodiment, fill
plug 220 may be in the form of a stainless steel ball bearing.
[0276] Referring to FIG. 91, in general, a fluid (not shown) is loaded through a fill hole
214-1 in body 214 into a sealed region, i.e., a fluid reservoir 228, between body
214 and diaphragm 222. Back pressure in fluid reservoir 228 is set and then maintained
by inserting, e.g., pressing, fill plug 220 into fill hole 214-1 to prevent air from
leaking into fluid reservoir 228 or fluid from leaking out of fluid reservoir 228.
End cap 218 is then placed onto an end of the body 214/lid 216 combination, opposite
to ejection chip 118. Stir bar 224 resides in the sealed fluid reservoir 228 between
body 214 and diaphragm 222 that contains the fluid. An internal fluid flow may be
generated within fluid reservoir 228 by rotating stir bar 224 so as to provide fluid
mixing and redistribution of particulate within the sealed region of fluid reservoir
228.
[0277] Referring now also to FIGs. 93 and 94, body 214 of housing 212 has a base wall 230
and an exterior perimeter wall 232 contiguous with base wall 230. Exterior perimeter
wall 232 is oriented to extend from base wall 230 in a direction that is substantially
orthogonal to base wall 230. Referring also to FIGs. 91 and 92, lid 216 is configured
to engage exterior perimeter wall 232. Thus, exterior perimeter wall 232 is interposed
between base wall 230 and lid 216, with lid 216 being attached to the open free end
of exterior perimeter wall 232 by weld, adhesive, or other fastening mechanism, such
as a snap fit or threaded union.
[0278] Referring to FIGs. 91-94, exterior perimeter wall 232 of body 214 includes an exterior
wall 232-1, which is a contiguous portion of exterior perimeter wall 232. Exterior
wall 232-1 has a chip mounting surface 232-2 and a fluid opening 232-3 adjacent to
chip mounting surface 232-2 that passes through the thickness of exterior wall 232-1.
[0279] Referring to FIGs. 92-94, chip mounting surface 232-2 defines a plane 234. Ejection
chip 118 is mounted, e.g., via an adhesive, to chip mounting surface 232-2 and is
in fluid communication with fluid opening 232-3 of exterior wall 232-1. The planar
extent of ejection chip 118 is oriented along the plane 234, with the plurality of
ejection nozzles 120 (see e.g., FIG. 1) oriented such that the fluid ejection direction
120-1 is substantially orthogonal to the plane 234. Base wall 230 is oriented along
a plane 236 that is substantially orthogonal to the plane 234 of exterior wall 232-1,
and is substantially parallel to the fluid ejection direction 120-1 (see FIGs. 90
and 93).
[0280] As illustrated in FIGs. 91-94, body 214 of housing 212 includes a chamber 238 located
within a boundary defined by exterior perimeter wall 232. Chamber 238 forms a portion
of fluid reservoir 228, and is configured to define an interior space, and in particular,
includes base wall 230 and has an interior perimetrical wall 240 configured to have
rounded corners, so as to promote fluid flow in chamber 238. Stir bar 224 is laterally
and longitudinally located by guide portion 226 within fluid reservoir 228 and within
a boundary defined by interior perimetrical wall 240, wherein guide portion 226 facilitates
movement of stir bar 224 in at least one direction substantially perpendicular to
the rotational axis 250 of stir bar 224.
[0281] Referring to FIGs. 92-94, interior perimetrical wall 240 of chamber 238 has an extent
bounded by a proximal end 240-1 and a distal end 240-2. Proximal end 240-1 is contiguous
with, and preferably forms a transition radius with, base wall 230. Distal end 240-2
is configured to define a perimetrical end surface 240-3 at an open end 238-1 of chamber
238. Perimetrical end surface 240-3 may include a plurality of ribs, or undulations,
to provide an effective sealing surface for engagement with diaphragm 222. The extent
of interior perimetrical wall 240 of chamber 238 is substantially orthogonal to base
wall 230, and is substantially parallel to the corresponding extent of exterior perimeter
wall 232.
[0282] Referring to FIGs. 95 and 96, chamber 238 has an inlet fluid port 242 and an outlet
fluid port 244, each of which is formed in a portion of interior perimetrical wall
240. Inlet fluid port 242 is separated a distance from outlet fluid port 244 along
the portion of interior perimetrical wall 240. The terms "inlet" and "outlet" are
terms of convenience that are used in distinguishing between the multiple ports of
the present embodiment, and are correlated with a particular rotational direction
250-1 of stir bar 224. However, it is to be understood that it is the rotational direction
of stir bar 224 that dictates whether a particular port functions as an inlet port
or an outlet port, and it is within the scope of this invention to reverse the rotational
direction of stir bar 224, and thus reverse the roles of the respective ports within
chamber 238.
[0283] As best shown in FIG. 96, body 214 of housing 212 includes a fluid channel 246 interposed
between a portion of interior perimetrical wall 240 of chamber 238 and exterior wall
232-1 of exterior perimeter wall 232 that carries ejection chip 118. Fluid channel
246 is configured to minimize particulate settling in a region of fluid opening 232-3,
and in turn, ejection chip 118.
[0284] In the present embodiment, fluid channel 246 is configured as a U-shaped elongated
passage having a channel inlet 246-1 and a channel outlet 246-2. Fluid channel 246
dimensions, e.g., height and width, and shape are selected to provide a desired combination
of fluid flow and fluid velocity for facilitating intra-channel stirring.
[0285] Fluid channel 246 is configured to connect inlet fluid port 242 of chamber 238 in
fluid communication with outlet fluid port 244 of chamber 238, and also connects fluid
opening 232-3 of exterior wall 232-1 of exterior perimeter wall 232 in fluid communication
with both inlet fluid port 242 and outlet fluid port 244 of chamber 238. In particular,
channel inlet 246-1 of fluid channel 246 is located adjacent to inlet fluid port 242
of chamber 238 and channel outlet 246-2 of fluid channel 246 is located adjacent to
outlet fluid port 244 of chamber 238. In the present embodiment, the structure of
inlet fluid port 242 and outlet fluid port 244 of chamber 238 is symmetrical. Each
of inlet fluid port 242 and outlet fluid port 244 of chamber 238 may have a beveled
ramp structure configured such that each of inlet fluid port 242 and outlet fluid
port 244 converges in a respective direction toward fluid channel 246.
[0286] Fluid channel 246 has a convexly arcuate wall 246-3 that is positioned between channel
inlet 246-1 and channel outlet 246-2, with fluid channel 246 being symmetrical about
a channel mid-point 248. In turn, convexly arcuate wall 246-3 of fluid channel 246
is positioned between inlet fluid port 242 and outlet fluid port 244 of chamber 238
on the opposite side of interior perimetrical wall 240 from the interior space of
chamber 238, with convexly arcuate wall 246-3 positioned to face fluid opening 232-3
of exterior wall 232-1 and fluid ejection chip 118.
[0287] Convexly arcuate wall 246-3 is configured to create a fluid flow substantially parallel
to ejection chip 118. In the present embodiment, a longitudinal extent of convexly
arcuate wall 246-3 has a radius that faces fluid opening 232-3, is substantially parallel
to ejection chip 118, and has transition radii 246-4, 246-5 located adjacent to channel
inlet 246-1 and channel outlet 246-2 surfaces, respectively. The radius and radii
of convexly arcuate wall 246-3 help with fluid flow efficiency. A distance between
convexly arcuate wall 246-3 and fluid ejection chip 118 is narrowest at the channel
mid-point 248, which coincides with a mid-point of the longitudinal extent of fluid
ejection chip 118, and in turn, with at a mid-point of the longitudinal extent of
fluid opening 232-3 of exterior wall 232-1.
[0288] Referring again to FIG. 91, diaphragm 222 is positioned between lid 216 and perimetrical
end surface 240-3 of interior perimetrical wall 240 of chamber 238. The attachment
of lid 216 to body 214 compresses a perimeter of diaphragm 222 thereby creating a
continuous seal between diaphragm 222 and body 214, and more particularly, diaphragm
222 is configured for sealing engagement with perimetrical end surface 240-3 of interior
perimetrical wall 240 of chamber 238 in forming fluid reservoir 228. Thus, in combination,
chamber 238 and diaphragm 222 cooperate to define fluid reservoir 228 having a variable
volume.
[0289] An exterior surface of diaphragm 222 is vented to the atmosphere through a vent hole
216-1 located in lid 216 so that a controlled negative pressure can be maintained
in fluid reservoir 228. Diaphragm 222 is made of rubber, and includes a dome portion
222-1 configured to progressively collapse toward base wall 230 as fluid is depleted
from microfluidic dispensing device 210, so as to maintain a desired negative pressure
in chamber 238, and thus changing the effective volume of the variable volume of fluid
reservoir 228.
[0290] Referring to FIG. 91, stir bar 224 resides, and is confined within, in the variable
volume of fluid reservoir 228 and in chamber 238, and is located within a boundary
defined by interior perimetrical wall 240 of chamber 238. Referring also to FIGs.
92-94 and 96-100, stir bar 224 has a rotational axis 250 and a plurality of paddles
252, 254, 256, 258 that radially extend away from the rotational axis 250. Stir bar
224 has a magnet 260 (see FIGs. 91, 96, and 100), e.g., a permanent magnet, configured
for interaction with external magnetic field generator 164 (see FIG. 1) to drive stir
bar 224 to rotate around the rotational axis 250. In the present embodiment, stir
bar 224 has two pairs of diametrically opposed paddles that are equally spaced at
90 degree increments around rotational axis 250. However, the actual number of paddles
of stir bar 224 is two or more, and preferably three or four, but more preferably
four, with each adjacent pair of paddles having the same angular spacing around the
rotational axis 250. For example, a stir bar 224 configuration having three paddles
would have a paddle spacing of 120 degrees, having four paddles would have a paddle
spacing of 90 degrees, etc.
[0291] In the present embodiment, as shown in FIGs. 91-94 and 97-100, stir bar 224 is configured
in a stepped, i.e., two-tiered, cross pattern with chamfered surfaces which may provide
the following desired attributes: quiet, short, low axial drag, good rotational speed
transfer, and capable of starting to mix with stir bar 224 in particulate sediment.
In particular, referring to FIG. 99, each of the plurality of paddles 252, 254, 256,
258 of stir bar 224 has an axial extent 262 having a first tier portion 264 and a
second tier portion 266. Referring also to FIG. 98, first tier portion 264 has a first
radial extent 268 terminating at a first distal end tip 270. Second tier portion 266
has a second radial extent 272 terminating in a second distal end tip 274. The first
radial extent 268 is greater than the second radial extent 272, such that a first
rotational velocity of first distal end tip 270 of first tier portion 264 is higher
than a second rotational velocity of second distal end tip 274 of second tier portion
266, while the angular velocity of first distal end tip 270 of first tier portion
264 is the same as the angular velocity of second distal end tip 274 of second tier
portion 266.
[0292] First tier portion 264 has a first tip portion 270-1 that includes first distal end
tip 270. First tip portion 270-1 may be tapered in a direction from the rotational
axis 250 toward first distal end tip 270. First tip portion of 270-1 of first tier
portion 264 has symmetrical upper and lower surfaces, each having a beveled, i.e.,
chamfered, leading surface and a beveled trailing surface. The beveled leading surfaces
and the beveled trailing surfaces of first tip portion 270-1 are configured to converge
at first distal end tip 270.
[0293] Also, in the present embodiment, first tier portion 264 of each of the plurality
of paddles 252, 254, 256, 258 collectively form a convex surface 276 (see FIGs. 91,
99 and 100). As shown in FIG. 91, convex surface 276 has a drag-reducing radius positioned
to contact base wall 230 of chamber 238. The drag-reducing radius may be, for example,
at least three times greater than the first radial extent 268 of first tier portion
264 of each of the plurality of paddles 252, 254, 256, 258.
[0294] Referring again to FIG. 99, second tier portion 266 has a second tip portion 274-1
that includes second distal end tip 274. Second distal end tip 274 may have a radial
blunt end surface. Second tier portion 266 of each of the plurality of paddles 252,
254, 256, 258 has an upper surface having a beveled, i.e., chamfered, leading surface
and a beveled trailing surface.
[0295] Referring to FIGs. 91-94, the orientation of stir bar 224 is achieved by guide portion
226, with guide portion 226 also being located within chamber 238 in the variable
volume of fluid reservoir 228, and more particularly, within the boundary defined
by interior perimetrical wall 240 of chamber 238. Guide portion 226 is configured
to confine and position stir bar 224 for movement in a predetermined portion of the
interior space of chamber 238.
[0296] Referring to FIGs. 91-94 and 96, guide portion 226 includes a confining member 279,
and a plurality of mounting arms 280-1, 280-2, 280-3, 280-4 coupled to confining member
279. Confining member 279 has a guide opening 279-1, which in the present embodiment
is in the form of an elongated opening 279-1, that defines an interior radial confining
surface 279-2 that limits, yet facilitates, radial movement of stir bar 224 in a direction
substantially perpendicular to rotational axis 250. While in the present embodiment
the longitudinal extent of elongated opening 279-1 is linear, those skilled in the
art will recognize that the longitudinal extent of elongated opening 279-1 may have
other non-linear shapes, such as S-shaped or C-shaped.
[0297] Referring particularly to FIGs. 92 and 94, elongated opening 279-1 has a longitudinal
extent 283-1 and a lateral extent 283-2 perpendicular to longitudinal extent 283-1.
Longitudinal extent 283-1 is greater, i.e., longer, than lateral extent 283-2. In
the present embodiment, longitudinal extent 283-1 is in a direction toward inlet and
outlet fluid ports 242, 244; fluid channel 246; and fluid opening 232-3 of exterior
wall 232-1 of body 214 of housing 212, so as to facilitate movement of stir bar 224
toward or away from inlet and outlet fluid ports 242, 244; fluid channel 246; fluid
opening 232-3; and ejection chip 118.
[0298] In particular, second tier portion 266 of stir bar 224 is received in elongated opening
279-1 of confining member 279. Interior radial confining surface 279-2 of elongated
opening 279-1 is configured to contact the radial extent of second tier portion 266
of the plurality of paddles 252, 254, 256, 258 of stir bar 224 to limit, yet facilitate,
radial (e.g., lateral and/or longitudinal) movement of stir bar 224 relative to rotational
axis 250 of stir bar 224. A maximum distance 283-3 between stir bar 224 and interior
radial confining surface 279-2 along the longitudinal extent 283-1 of elongated opening
279-1 defines the longitudinal limit of motion of stir bar 224 within chamber 238.
[0299] In the present example, the lateral extent 283-2 of interior radial confining surface
279-2 of elongated opening 279-1 is only slightly larger (e.g., 0.5 to 5 percent)
than the diameter across the radial extent of second tier portion 266 of stir bar
224, whereas the longitudinal extent 283-1 of interior radial confining surface 279-2
of elongated opening 279-1 is substantially larger (e.g., greater than 10 percent)
than the diameter across the radial extent of second tier portion 266 of stir bar
224, so as to facilitate radial movement of stir bar 224 in a direction substantially
perpendicular to rotational axis 250 of stir bar 224 along the longitudinal extent
283-1 of interior radial confining surface 279-2 of elongated opening 279-1. In other
words, in the present example, stir bar 224 is permitted to slide back and forth along
the longitudinal extent 283-1 of interior radial confining surface 279-2 of elongated
opening 279-1.
[0300] Referring to FIGs. 91 and 96, confining member 279 has an axial confining surface
279-3 positioned to be axially offset from base wall 230 of chamber 238, for axial
engagement with first tier portion 264 of stir bar 224.
[0301] Referring to FIGs. 93-96, the plurality of mounting arms 280-1, 280-2, 280-3, 280-4
are configured to engage body 214 of housing 212 to position, e.g., suspend, confining
member 279 in the interior space of chamber 238, separated from base wall 230 of chamber
238, with axial confining surface 279-3 positioned to face, and to be axially offset
from, base wall 230 of chamber 238. A distal end of each of mounting arms 280-1, 280-2,
280-3, 280-4 includes respective locating features 280-5, 280-6, 280-7, 280-8 that
have free ends to engage a perimetrical portion of diaphragm 222 (see also FIG. 91).
[0302] In the present embodiment, referring to FIGs. 91 and 96, base wall 230 limits axial
movement of stir bar 224 relative to the rotational axis 250 in a first axial direction
and axial confining surface 279-3 of confining member 279 is located to axially engage
at least a portion of first tier portion 264 of the plurality of paddles 252, 254,
256, 258 to limit axial movement of stir bar 224 relative to the rotational axis 250
in a second axial direction opposite to the first axial direction.
[0303] As such, in the present embodiment, stir bar 224 is radially confined within the
region defined by interior radial confining surface 279-2 of elongated opening 279-1
of confining member 279, and is axially confined between axial confining surface 279-3
of confining member 279 and base wall 230 of chamber 238. The portion of chamber 238
and fluid reservoir 228 in which stir bar 224 is moveable is determined by the location
of elongated opening 279-1 of guide portion 226 in chamber 238. The extent to which
stir bar 224 is moveable within chamber 238 and fluid reservoir 228 is determined
by the radial tolerances provided between interior radial confining surface 279-2
of elongated opening 279-1 of guide portion 226 and stir bar 224 in a radial direction
perpendicular to rotational axis 250, and by the axial tolerances between stir bar
224 and the axial limit provided by the combination of base wall 230 and axial confining
surface 279-3 of confining member 279. For example, the tighter the radial and axial
tolerances provided by guide portion 226, the less variation of the rotational axis
250 of stir bar 224 from perpendicular relative to base wall 230, and the less side-to-side
motion of stir bar 224 within fluid reservoir 228.
[0304] Notwithstanding, the longitudinal extent 283-1 of elongated opening 279-1 of confining
member 279 facilitates radial movement of stir bar 224 in a direction substantially
perpendicular to rotational axis 250 of stir bar 224 in at least one direction, e.g.,
in at least a longitudinal direction corresponding to the longitudinal extent 283-1
of elongated opening 279-1. Referring to FIGs. 92 and 94, a maximum distance 283-3
between stir bar 224 and interior radial confining surface 279-2 along the longitudinal
extent 283-1 of elongated opening 279-1 defines the longitudinal limit of motion of
stir bar 224 within chamber 238.
[0305] In view of the above, those skilled in the art will recognize that lateral motion
of stir bar 224 may be facilitated by increasing lateral extent 283-2 of elongated
opening 279-1 of guide portion 226, such that a gap is present between stir bar 224
and interior radial confining surface 279-2 along the lateral extent 283-2 of elongated
opening 279-1 of confining member 279 of guide portion 226. As such, in addition to
linear movement of rotational axis 250 of stir bar 224 being facilitated, other movement
patterns, such as other linear patterns, e.g., diagonal, X-shaped, Z-shaped, etc.,
or non-linear, such as curved, circular, elliptical, a figure 8 pattern, etc., may
be realized.
[0306] In accordance with the present invention, to effect movement of the location of stir
bar 224 within fluid reservoir 228, first, external magnetic field generator 164 (see
FIG. 1) is energized to interact with magnet 260 (see FIGs. 91 and 96), e.g., a permanent
magnet, of stir bar 224. If the magnetic field generated by external magnetic field
generator 164 is rotating, then stir bar 224 will tend to rotate in unison with the
rotation of the magnetic field. Next, housing 212 of microfluidic dispensing device
210 is moved relative to external magnetic field generator 164, or vice versa. In
other words, magnet 260 of stir bar 224 is attracted to the magnetic field generated
by external magnetic field generator 164, such that the rotational axis 250 of stir
bar 224 will be relocated within fluid reservoir 228 with a change of location of
external magnetic field generator 164 relative to the location of housing 212 of microfluidic
dispensing device 210.
[0307] In the present embodiment, guide portion 226 is configured as a unitary insert member
that is removably received in housing 212. Referring to FIG. 96, guide portion 226
includes a first retention feature 284 and body 214 of housing 212 includes a second
retention feature 214-2. First retention feature 284 is engaged with second retention
feature 214-2 to attach guide portion 226 to body 214 of housing 212 in a fixed relationship
with housing 212. First retention feature 284/second retention feature 214-2 combination
may be, for example, in the form of a tab/slot arrangement, or alternatively, a slot/tab
arrangement, respectively.
[0308] Referring to FIG. 96, guide portion 226 may further include a flow control portion
286 having a flow separator feature 286-1, a flow rejoining feature 286-2, and a concavely
arcuate surface 286-3. Flow control portion 286 provides an axial spacing between
axial confining surface 279-3 and base wall 230 in the region of inlet fluid port
242 and outlet fluid port 244. Concavely arcuate surface 286-3 is coextensive with,
and extends between, each of flow separator feature 286-1 and flow rejoining feature
286-2. Flow separator feature 286-1 is positioned adjacent inlet fluid port 242 and
flow rejoining feature 286-2 is positioned adjacent outlet fluid port 244. Flow separator
feature 286-1 has a beveled wall that cooperates with inlet fluid port 242 of chamber
238 to guide fluid toward channel inlet 246-1 of fluid channel 246. Likewise, flow
rejoining feature 286-2 has a beveled wall that cooperates with outlet fluid port
244 to guide fluid away from channel outlet 246-2 of fluid channel 246.
[0309] It is contemplated that all, or a portion, of flow control portion 286 may be incorporated
into interior perimetrical wall 240 of chamber 238 of body 214 of housing 212.
[0310] In the present embodiment, as is best shown in FIG. 96, stir bar 224 is oriented
such that the free ends of the plurality of paddles 252, 254, 256, 258 periodically
face concavely arcuate surface 286-3 of flow control portion 286 as stir bar 224 is
rotated about the rotational axis 250. More particularly, guide portion 226 is configured
to confine stir bar 224 in a predetermined portion of the interior space of chamber
238. In the present example, elongated opening 279-1 of confining member 279 of guide
portion 226 facilitates radial movement of stir bar 224 in a direction toward, or
away from, concavely arcuate surface 286-3 of flow control portion 286 and toward,
or away from, inlet and outlet fluid ports 242, 244; fluid channel 246; and fluid
opening 232-3 in at least a longitudinal direction corresponding to the longitudinal
extent 283-1 of elongated opening 279-1 (see FIGs. 92 and 94).
[0311] More particularly, in the present embodiment wherein stir bar 224 has four paddles,
guide portion 226 is configured to position the rotational axis 250 of stir bar 224
in a portion of the interior space of chamber 238 such that first distal end tip 270
of each the two pairs of diametrically opposed paddles alternatingly and intermittently
are positioned to face in a direction toward inlet and outlet fluid ports 242, 244;
fluid channel 246; and fluid opening 232-3, as stir bar 224 is rotated.
[0312] Those skilled in the art will recognize that the actual configuration of stir bar
224 may be modified in various ways, without departing from the scope of the present
invention. For example, it is contemplated that shape and/or size of the plurality
of paddles of stir bar 224 may be varied from the express example set forth herein.
Also, it is contemplated that second tier portion 266 of stir bar 224 (see FIG. 99)
may be formed as a continuous circular hub.
[0313] While this invention has been described with respect to at least one embodiment,
the present invention can be further modified within the spirit and scope of this
disclosure. This application is therefore intended to cover any variations, uses,
or adaptations of the invention using its general principles. Further, this application
is intended to cover such departures from the present disclosure as come within known
or customary practice in the art to which this invention pertains and which fall within
the limits of the appended claims.