TECHNICAL FIELD OF THE INVENTION
[0001] The present invention relates to manipulation of particles in a sample fluid by use
of dielectrophoresis. More particularly, the present invention relates to a dielectrophoretic
device for manipulation of at least two different types of particles present in a
sample fluid, to a method for forming such a dielectrophoretic device, to a method
for manipulating at least two different types of particles in a sample fluid by using
dielectrophoresis and to a controller for controlling driving of electrodes of a dielectrophoretic
device.
BACKGROUND OF THE INVENTION
[0002] Lab-on-a-chip techniques require a combination of electronic and biological expertise
to obtain a fully integrated electronic system. Achieving such fully integrated electronic
system requires dedicated systems within the chip, such as systems for sample preparation,
polymerised chain reaction (PCR) and target detection. Therefore, there is a strong
drive to find an accurate method to reliably pass fluids and essay samples around
the miniature lab, especially without introducing contaminates.
[0003] One of the methods to achieve this is through electrical manipulation of bio-molecules
or particles, which is called dielectrophoresis (DEP), i.e. the movement of dielectric
particles in a non-uniform, usually AC, electric field. Unlike electrophoresis, DEP
relies on field-induced polarization effects and is independent of the net charge
of particles present in the fluids. The DEP force depends on the electrical properties
of the particles and of the surrounding medium, on the size and shape of the particles
and on the spatial distribution and frequency of the applied field. Depending on these
factors, the particles can be attracted to either high-field (positive DEP) or low-field
(negative DEP) regions. By using proper electrode configurations and multiphase fields,
DEP can be used to levitate particles, trap them in a field cage, rotate them (electro-rotation)
or transport them over relatively long distances (traveling wave DEP).
[0004] DEP thus enables, amongst others, transportation, focusing, purification and/or mixing
of fluids. This technique also can be applied to locally enhance the performance of
biosensors within the lab-on-a-chip. DEP has in the past been applied to manipulate
and separate a variety of cells including bacteria, yeast, and mammalian cells in
microsystems. In particular, DEP has been used to separate cancer cells from blood,
isolate CD34+ stem cells from blood, bacteria from blood and to separate various cell
sub-populations of blood.
[0005] It has thus been shown that electrical manipulation of fluids and biomolecules can
be achieved by using DEP; however, the differentiation between the contents of mixed
samples can be difficult. To make Lab-on-a-Chip techniques into a success, methods
to solve this differentiation/filtering problem have to be found.
[0006] Other techniques to sort particles of different types, for example techniques developed
by the University of Southampton (Hywel Morgan), require an optical feedback process
to adjust electrical fields which are exerted onto the particle or particles of interest.
A disadvantage of this technique and of other microfluidic channelling techniques
is that they can only operate on a single biomolecule at a time and therefore the
throughput of material may be slowed down to a great extent. For example, if a sample
comprises 1 million particles and the optical/electrical control system only has a
throughput of 10 to 100 particles per second, it may take up to a few hours before
the sample has completely been examined. With DEP there is no loss in transport speed.
This is because the movement of all particles over the electrodes can occur at once.
Therefore the throughput of bio-matter can be orders of magnitudes larger than for
other existing techniques. However, the specificity of being able to assess each cell
has been lost as all cells will move together and any manipulation of the cells will
be applied to all of the cells.
SUMMARY OF THE INVENTION
[0007] It is an object of embodiments of the present invention to provide a good dielectrophoretic
device for manipulation of at least two different types of particles present in a
sample fluid, and a method for manipulating at least two different types of particles
in a sample fluid by using such a dielectrophoretic device.
[0008] The dielectrophoretic device and methods according to embodiments of the invention
are able to provide a good selectivity between at least two particles that have similar
dielectric properties or Clausius-Mossotti responses by spatially amplifying a subtle
difference between the DEP characteristics of the particles of interest, while keeping
high throughput capabilities.
[0009] The dielectrophoretic device and methods according to embodiments of the present
invention address purification of particles without the loss of transportation efficiency.
[0010] The dielectrophoretic device and methods according to embodiments of the invention
may be used in a variety of applications where particle sorting, e.g. cell sorting,
particle manipulation, e.g. cell manipulation, filtering, ordering, and/or transportation
is important. Such applications may include molecular diagnostics, biological sample
analysis or chemical sample analysis.
[0011] The dielectrophoretic device and method according to embodiments of the present invention
can be used in Lab-on-a-Chip techniques for manipulation, e.g. moving or sorting,
of particles such as cells on a microscopic scale, or cells or molecules which are
attached to particles, such as magnetic beads. The dielectrophoretic device and method
according to embodiments of the present invention can furthermore be combined with
other sorting and filtering systems.
[0012] The dielectrophoretic device and method according to embodiments of the present invention
may be used to improve results of biological experiments. For example, the dielectrophoretic
device and method according to embodiments of the present invention may be used to
obtain a good efficiency in cell lysing, to improve the obtainable quantity of amplicons
for specific polymer chain reaction (PCR) experiments and to improve detection of
hybridised DNA.
[0013] The above objective is accomplished by a method and device according to the present
invention.
[0014] In a first aspect, the present invention provides a dielectrophoretic device for
manipulation of at least a first and a second type of particles present in a sample
fluid. The device comprises:
- at least one array of electrodes, the array comprising at least a plurality of electrodes
in a first region and a plurality of electrodes in a second region,
- driving means for driving the electrodes of the first and second region of the array
to generate a travelling wave dielectrophoretic force to be exerted on the at least
first and second types of particles, and
- a controller for controlling the driving means, the controller being adapted for first
driving the electrodes of the first and second region with a same driving signal and
subsequently changing the driving signal to electrodes of at least one of the first
and second region so as to separate at least some particles of the first type from
the particles of the second type.
[0015] The device according to embodiments of the invention may be used in a variety of
applications including molecular diagnostics, biological sample analysis or chemical
sample analysis. The dielectrophoretic device according to embodiments of the present
invention may be used to improve results of biological experiments. For example, the
dielectrophoretic device according to embodiments of the present invention may be
used to obtain a good efficiency in cell lysing, to improve the obtainable quantity
of amplicons for specific polymer chain reaction (PCR) experiments and to improve
detection of hybridised DNA.
[0016] The device for manipulation of particles according to embodiments of the present
invention only relies on electrical field induced effects in order to achieve manipulation
of particles, e.g. separation of particles, on a macroscopic level. In a device according
to embodiments of the invention, particles, e.g. cells are transported electrically
through a stationary fluid. Therefore, in accordance with embodiments of the present
invention, the need for liquid flow generation and thus for pumping mechanisms, may
be eliminated. This allows, in principle, using very small volumes of suspensions
comprising the particles. The dielectrophoretic device according to embodiments of
the invention can be used for performing particle manipulation from small, non-flowing
volumes of particle suspensions. With small volumes is meant volumes of between 0.5
and 50 µl, for example 10 µl.
[0017] According to embodiments of the invention, the controller may be adapted for changing
the driving signal to electrodes of at least one of the first and second region upon
reaching of a boundary between the first and second region of the array of electrodes
by a predetermined one of the at least first and second type of particles.
[0018] The dielectrophoretic device may furthermore comprise collection means for collecting
at least one of the first and second type of particles which have crossed the boundary
between the first and second region of the array of electrodes. According to embodiments,
the collected particles may then further be used to perform experiments on. According
to other embodiments, the collected particles may, for example, be counted.
[0019] The collection means may be formed by a dielectrophoretic trap.
[0020] According to embodiments of the invention, the dielectrophoretic device may furthermore
comprise transport means for transporting collected particles towards other regions
of the dielectrophoretic device, or optionally away from the device, so as to enable
focusing of selected particles. This may allow continued particle movement into further
regions of the dielectrophoretic device where they may be used for further reactions
or experiments, for example for cell lysing or for detection.
[0021] According to still further embodiments of the invention, the dielectrophoretic device
may furthermore comprise detection means for detecting reaching of the boundary between
the first and second region of the array of electrodes by the predetermined one of
the at least first and second type of particles.
[0022] According to embodiments of the invention, the detection means may be an optical
detection means such as e.g. an optical detector, e.g. integrated PIN diodes.
[0023] According to other embodiments of the invention, the detection means may be a time
determination means.
[0024] According to still other embodiments of the invention, the detection means may be
means for determining a predetermined volume of at least one of the first and second
type of particles which have passed the boundary between the first and second region
of the array of electrodes.
[0025] According to embodiments of the invention, the dielectrophoretic device may comprise
a cascade of arrays of electrodes. This may enhance the efficiency of the manipulation
process to a great extent while still maintaining a high throughput of particles.
Each array of the cascade may be driven one after the other, and in that way may result
in a high degree of separation between the first and second particles present in the
sample fluid.
[0026] In a further aspect, the present invention also provides the use of the dielectrophoretic
device according to embodiments of the present invention for particle separation or
sorting.
[0027] In still a further aspect of the invention, a method is provided for forming a dielectrophoretic
device for manipulation of at least a first and second type of particles in a sample
fluid. The method comprises:
- providing at least one array of electrodes, the array comprising at least a plurality
of electrodes in a first region and a plurality of electrodes in a second region,
- providing driving means for driving the electrodes of the first and second region
of the array to generate a travelling wave dielectrophoretic force to be exerted on
the at least first and second types of particles, and
- providing a controller for controlling the driving means, the controller being adapted
for first driving the electrodes of the first and second region with a same driving
signal and subsequently changing the driving signal to electrodes of at least one
of the first and second region so as to separate at least some particles of the first
type from the particles of the second type.
[0028] The method may furthermore comprise providing collection means for collecting at
least one of the first and second type of particles which have crossed a boundary
between the first and second region of the array of electrodes.
[0029] The method may furthermore comprise providing transport means for transporting collected
particles towards other regions of the dielectrophoretic device, or optionally away
from the device, so as to enable focusing of selected particles.
[0030] The method may furthermore comprise providing detection means for detecting reaching
of the boundary between the first and second region by a predetermined one of the
at least first and second type of particles. The detection means may be an optical
detection means, a time determination means or a means for determining a predetermined
volume of at least one of the first and second type of particles which have passed
the boundary between the first and second region of the array of electrodes.
[0031] Providing at least one array of electrodes may be performed by providing a cascade
of arrays. Each array of the cascade may be provided such that it may be driven one
after the other, which may result in a high degree of separation between the first
and second particles present in the sample fluid.
[0032] In yet a further aspect, the present invention provides a method for manipulating
at least a first and second type of particles in a sample fluid. The method comprises:
- a) providing sample fluid comprising the at least first and second type of particles
to a microfluidic device comprising at least one array of electrodes, the array comprising
at least a plurality of electrodes in a first region and a plurality of electrodes
in a second region,
- b) applying a same driving signal to electrodes of the first and second regions, the
driving signal being such that the first type of particles and the second type of
particles move with a different speed, and
- c) subsequently changing the driving signal to electrodes of at least one of the first
and second regions so as to separate at least some particles of the first type from
the particles of the second type.
[0033] The method according to embodiments of the invention may be used in a variety of
applications including molecular diagnostics, biological sample analysis or chemical
sample analysis. The method according to embodiments of the present invention may
be used to improve results of biological experiments. For example, the method according
to embodiments of the present invention may be used to obtain a good efficiency in
cell lysing, to improve the obtainable quantity of amplicons for specific polymer
chain reaction (PCR) experiments or to improve detection of hybridised DNA.
[0034] The method for manipulation of particles according to embodiments of the present
invention only relies on electrical field induced effects in order to achieve manipulation
of particles, e.g. separation of particles, on a macroscopic level. In a method according
to embodiments of the invention, particles, e.g. cells, are transported electrically
through a stationary fluid. Therefore, in accordance with embodiments of the present
invention, the need for liquid flow generation and thus for pumping mechanisms, may
be eliminated. This allows, in principle, using very small volumes of suspensions
comprising the particles. With very small volumes is meant volumes of between 0.5
and 50 µl, for example 10 µl.
[0035] The method may furthermore comprise, before changing the driving signal to electrodes
of at least one of the first and second region, determining whether a predetermined
one of the first and second type of particles has reached a boundary between the first
and second region of the array of electrodes.
[0036] According to embodiments of the invention, determining whether a predetermined one
of the first and second type of particles has reached the boundary between the first
and second region of the array of electrodes may be performed by an optical detection
means, for example with an optical detector, e.g. with integrated PIN diodes.
[0037] According to other embodiments of the invention, determining whether a predetermined
one of the first and second type of particles has reached the boundary between the
first and second region of the array of electrodes may be performed by means of calculating
a time period required for the predetermined one of the first and second type of particles
to reach the boundary between the first and second region of the array of electrodes.
[0038] According to embodiments of the invention the method may furthermore comprise repeating
steps b and c of applying and changing the driving signal at least once. Repeating
steps b and c may be performed as many times as necessary for obtaining good manipulation
of the particles, for example for obtaining good separation between a first and second
type of particles.
[0039] The method may furthermore comprise collecting at least one of the first and second
type of particles which have crossed the boundary between the first and second region
of the array of electrodes. According to embodiments, the collected particles may
then further be used to perform experiments on.
[0040] The method may furthermore comprise detecting the collected particles. According
to other embodiments, the collected particles may, for example, be counted.
[0041] In a further aspect of the invention, a controller is provided for controlled driving
of electrodes of an array, the array comprising at least a plurality of electrodes
in a first region and a plurality of electrodes in a second region. The controller
comprises a control unit for controlling a driving means for first driving the electrodes
of the first and second region with a same driving signal and subsequently changing
the driving signal to electrodes of at least one of the first and second region so
as to separate at least some particles of the first type from the particles of the
second type.
[0042] The controller may be adapted for changing the driving signal to electrodes of at
least one of the first and second region upon reaching of the boundary between the
first and second region of the array of electrodes by a predetermined one of the at
least first and second type of particles.
[0043] The present invention also provides a computer program product for performing, when
executed on a computing means, a method for manipulating at least a first and second
type of particles in a sample fluid according to embodiments of the present invention.
[0044] The present invention also provides a machine readable data storage device for storing
the computer program product according to embodiments of the present invention.
[0045] The present invention also provides a transmission of the computer program product
according to embodiments of the present invention over a local or wide area telecommunications
network.
[0046] Particular and preferred aspects of the invention are set out in the accompanying
independent and dependent claims. Features from the dependent claims may be combined
with features of the independent claims and with features of other dependent claims
as appropriate and not merely as explicitly set out in the claims.
[0047] The above and other characteristics, features and advantages of the present invention
will become apparent from the following detailed description, taken in conjunction
with the accompanying drawings, which illustrate, by way of example, the principles
of the invention. This description is given for the sake of example only, without
limiting the scope of the invention. The reference figures quoted below refer to the
attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0048]
Fig. 1 illustrates Clausius-Mossotti curves (upper graph) and velocity curves (lower
graph) for two different types of particles.
Fig. 2 and Fig.3 schematically illustrate the operation principle of a dielectrophoretic
device according to embodiments of the present invention.
Fig. 4 illustrates part of a configuration of a dielectrophoretic device according
to embodiments of the present invention.
Fig. 5 shows particle distribution curves after applying a same driving signal to
electrodes of a first and second region of a dielectrophoretic device according to
embodiments of the invention during a predetermined time period for a first and second
type of particles with different DEP properties.
Fig. 6 illustrates particle distribution curves for a first and second type of particles
with different DEP properties for different periods in time and for different number
of changes to the driving signals (different number of resets).
Fig. 7 illustrates concentration of a first type of particles (curve 26) and concentration
of a second type of particles 2 (curve 27) that have crossed a boundary between a
first and second region of a dielectrophoretic device according to embodiments of
the present invention as a function of the number of resets.
Fig. 8 illustrates part of a configuration of a dielectrophoretic device according
to embodiments of the present invention.
Fig. 9 illustrates part of a configuration of a dielectrophoretic device according
to embodiments of the present invention.
Fig. 10 and Fig. 11 illustrate driving of electrodes of an array of a dielectrophoretic
device according to embodiments of the present invention for obtaining travelling
wave dielectrophoresis.
Fig. 12 schematically illustrates a system controller for use with a dielectrophoretic
device according to embodiments of the present invention.
Fig. 13 is a schematic representation of a processing system as can be used for performing
a method according to embodiments of the present invention.
[0049] In the different figures, the same reference signs refer to the same or analogous
elements.
DETAILED DESCRIPTION OF THE INVENTION
[0050] The present invention will be described with respect to particular embodiments and
with reference to certain drawings but the invention is not limited thereto but only
by the claims. Any reference signs in the claims shall not be construed as limiting
the scope. The drawings described are only schematic and are non-limiting. In the
drawings, the size of some of the elements may be exaggerated and not drawn on scale
for illustrative purposes.
[0051] Where the term "comprising" is used in the present description and claims, it does
not exclude other elements or steps. Where an indefinite or definite article is used
when referring to a singular noun e.g. "a" or "an", "the", this includes a plural
of that noun unless something else is specifically stated.
[0052] Furthermore, the terms first, second and the like in the description and in the claims,
are used for distinguishing between similar elements and not necessarily for describing
a sequence, either temporally, spatially, in ranking or in any other manner. It is
to be understood that the terms so used are interchangeable under appropriate circumstances
and that the embodiments of the invention described herein are capable of operation
in other sequences than described or illustrated herein.
[0053] Reference throughout this specification to "one embodiment" or "an embodiment" means
that a particular feature, structure or characteristic described in connection with
the embodiment is included in at least one embodiment of the present invention. Thus,
appearances of the phrases "in one embodiment" or "in an embodiment" in various places
throughout this specification are not necessarily all referring to the same embodiment,
but may. Furthermore, the particular features, structures or characteristics may be
combined in any suitable manner, as would be apparent to one of ordinary skill in
the art from this disclosure, in one or more embodiments.
[0054] Similarly it should be appreciated that in the description of exemplary embodiments
of the invention, various features of the invention are sometimes grouped together
in a single embodiment, figure, or description thereof for the purpose of streamlining
the disclosure and aiding in the understanding of one or more of the various inventive
aspects. This method of disclosure, however, is not to be interpreted as reflecting
an intention that the claimed invention requires more features than are expressly
recited in each claim. Rather, as the following claims reflect, inventive aspects
lie in less than all features of a single foregoing disclosed embodiment. Thus, the
claims following the detailed description are hereby expressly incorporated into this
detailed description, with each claim standing on its own as a separate embodiment
of this invention.
[0055] Furthermore, while some embodiments described herein include some but not other features
included in other embodiments, combinations of features of different embodiments are
meant to be within the scope of the invention, and form different embodiments, as
would be understood by those in the art. For example, in the following claims, any
of the claimed embodiments can be used in any combination.
[0056] Furthermore, some of the embodiments are described herein as a method or combination
of elements of a method that can be implemented by a processor of a computer system
or by other means of carrying out the function. Thus, a processor with the necessary
instructions for carrying out such a method or element of a method forms a means for
carrying out the method or element of a method. Furthermore, an element described
herein of an apparatus embodiment is an example of a means for carrying out the function
performed by the element for the purpose of carrying out the invention.
[0057] In the description provided herein, numerous specific details are set forth. However,
it is understood that embodiments of the invention may be practiced without these
specific details. In other instances, well-known methods, structures and techniques
have not been shown in detail in order not to obscure an understanding of this description.
[0058] The present invention provides a dielectrophoretic device for manipulation of at
least a first and second type of particles present in a sample fluid, a method for
forming such a dielectrophoretic device, a method for manipulating at least a first
and second type of particles in a sample fluid and a controller for controlling driving
of electrodes of a dielectrophoretic device.
[0059] The dielectrophoretic device and methods according to embodiments of the present
invention address purification of particles such as e.g. bio-molecules without loss
of transportation efficiency as seen in existing systems.
[0060] The dielectrophoretic devices and methods according to embodiments of the invention
are able to provide a good selectivity between at least two particles that have similar
dielectric properties or Clausius-Mossotti curves by spatially amplifying a subtle
difference between the DEP characteristics of the particles of interest, while keeping
high throughput capabilities.
[0061] Particles, such as for example B-lymphocytes, T-lymphocytes and erythrocytes, present
in a sample fluid can exhibit similar dielectric properties or Clausius-Mossotti responses
at key frequencies, resulting in small velocity changes between the populations in
negative DEP (-ve DEP in Fig. 1). A Clausius-Mossotti curve gives the difference in
velocity for different particle properties. Fig. 1 illustrates Clausius-Mossotti curves
of two particles with similar properties (see upper graph, curve 20 for a first particle
and curve 21 for a second particle) and their velocities (lower graph, curve 22 for
the first particle and curve 23 for the second particle) while levitated above electrodes
in -ve DEP.
[0062] The two particles with similar properties in Figure 1 are "similar" in that one can
pick a frequency (e.g 10
5 Hz) and there is only a small difference in the velocity's. Normally in DEP, the
curves are separated by an order of magnitude in frequency, so that one is held fixed
in +DEP while the other levitates and travels in -DEP.
[0063] In this example, the curves in Figure 1 relate to B-lymphocytes and T-lymphocytes.
[0064] They are white cells, which are very hard to distinguish in a blood smear and optical
detection, even they are hard to distinguish with impedance spectroscopy.
[0065] Their differences in makeup are very slight, and are derived from the same small
lymphocyte parent cell. Their functions differ in that the B cell can develop into
a plasma cell for the secretion of antibodies, while the T cells release a range of
hormone proteins for communication in the event of an immune response.
[0066] In relation to the curve, the curves show a measure of polarisability of the proteins
in the cell and on the cell surface. In the case of a T and B cells, they are coated
in antigens, T cells explicitly exhibit an antigen protein called CD3 while B cells
do not.
[0067] The dielectrophoretic device and methods according to embodiments of the invention
may be used in a variety of applications where particle sorting, e.g. cell sorting,
particle manipulation, e.g. cell manipulation, filtering, ordering and/or transportation
is important. Such applications may include molecular diagnostics, biological sample
analysis or chemical sample analysis.
[0068] The dielectrophoretic device and methods according to embodiments of the present
invention can be used in Lab-on-a-Chip techniques for manipulation, e.g. moving or
sorting, of particles such as e.g. cells on a microscopic scale, or cells or molecules
which are attached to particles such as e.g. magnetic beads, and which can be combined
with other sorting and filtering systems.
[0069] The dielectrophoretic devices and methods according to embodiments of the present
invention may be used to improve results of biological experiments. For example, the
dielectrophoretic devices and methods according to embodiments of the present invention
may be used to obtain a good efficiency in cell lysing, to improve the obtainable
quantity of amplicons for specific polymer chain reaction (PCR) experiments and improve
detection of hybridised DNA.
[0070] The devices and methods according to embodiments of the invention may be used for
manipulation of dielectric particles such as microparticles, nanoparticles, cells,
or to any other kind of particles having dielectrophoretic properties. Examples of
suitable particles which may be used with embodiments of the present invention may
be solid dielectric particles such as e.g. polystyrene or latex beads or carrier beads
(beads to which molecules or cells can be bound), engineered particles such as e.g.
particles with a conductive core and an insulating shell, or vice versa, biological
particles such as cells, bacteria, viruses, DNA, RNA, large molecules e.g. large proteins,
complexes of molecules.
[0071] With manipulation of particles is, amongst others, meant transporting, sorting or
separating particles.
[0072] The sample fluid may be any kind of sample fluid known by a person skilled in the
art and may be a gas or a liquid. According to specific embodiments of the invention,
the fluid may, for example, be blood or saliva.
[0073] The device and method for manipulation of particles according to embodiments of the
present invention only rely on electrical field induced effects in order to achieve
manipulation of particles, e.g. separation of particles, on a macroscopic level. In
a device according to embodiments of the invention, particles, e.g. cells are transported
electrically through a stationary fluid. Therefore, in accordance with embodiments
of the present invention, the need for liquid flow generation and thus for pumping
mechanisms, may be eliminated. This allows, in principle, using very small volumes
of suspensions comprising the particles. The dielectrophoretic device and methods
according to embodiments of the invention can be used for performing particle manipulation
from small, non-flowing volumes of particle suspensions. With small volumes is meant
volumes of between 0.5 and 50 µl, for example 10 µl.
[0074] The devices and methods according to embodiments of the invention may, for example,
be used for separating or sorting particles with different dielectric properties.
Particle types may differ in size, shape and/or composition, which will lead to different
dielectric properties and thus to different dielectrophoretic responses.
[0075] In a first aspect of the present invention, a dielectrophoretic device is provided
for manipulation of at least a first and second type of particles present in a sample
fluid. The at least first and second type of particles are different from each other.
The device comprises:
- an array of electrodes, the array comprising at least a plurality of electrodes in
a first region and a plurality of electrodes in a second region,
- driving means for driving the electrodes of the first and second region of the array
to generate a travelling wave dielectrophoretic (twDEP) force to be exerted on the
at least first and second types of particles, and
- a controller for controlling the driving means, the controller being adapted for first
driving the electrodes of the first and second region with a same driving signal and
subsequently changing the driving signal to electrodes of at least one of the first
and second region so as to separate at least some particles of the first type from
the particles of the second type.
[0076] The present invention also provides, in another aspect, a method for manipulating
at least a first and second type of particles in a sample fluid. The method comprises:
- providing sample fluid comprising the at least first and second type of particles
to a microfluidic device comprising an array of electrodes, the array comprising at
least a plurality of electrodes in a first region and a plurality of electrodes in
a second region,
- applying a same driving signal to electrodes of the first and second regions, the
driving signal being such that the first type of particles and the second type of
particles move with a different speed, and
- subsequently changing the driving signal to electrodes of at least one of the first
and second region so as to separate at least some particles of the first type from
the particles of the second type.
[0077] Hereinafter, the dielectrophoretic device and method for manipulating at least a
first and second type of particles in a sample fluid according to embodiments of the
invention will be described by means of different embodiments.
[0078] Fig. 2 and Fig. 3 schematically illustrate the principle of a dielectrophoretic device
according to embodiments of the invention. This principle is illustrated based on
a sample fluid comprising two different types of particles 1, 2, e.g. larger and smaller
particles, or particles having a different weight. It has to be understood that this
is not intended to limit the invention in any way. The invention may also be applied
to manipulate any number of types of particles present in a sample fluid.
[0079] Fig. 2 and Fig. 3 illustrate two steps required to separate a mixture of a first
type of particles 1 and a second type of particles 2 present in a sample fluid. The
sample fluid may be a liquid or a gas. The dielectrophoretic device comprises an array
3 of electrodes 4. The array 3 comprises at least a plurality of electrodes 4 in a
first region 5 and a plurality of electrodes 4 in a second region 6, there being a
boundary 7 in between the first and second region 5, 6. The electrodes 4 may have
a longitudinal direction and the longitudinal direction of the electrodes 4 may be
substantially parallel to each other, both in the first region 5 and in the second
region 6. Also the longitudinal direction of the electrodes 4 in the first region
5 and in the second region 6 may be parallel to each other.
[0080] A driving signal is applied to the electrodes 4 in at least the first and second
regions 5, 6, for generating a travelling wave dielectrophoretic (twDEP) force to
the first and second type of particles 1, 2, so as to cause movement of the first
and second type of particles 1, 2. In a first step, which is illustrated in Fig. 2,
a same driving signal is applied to all electrodes 4, i.e. to the electrodes 4 of
the first and second region 5, 6 of the array 3. In this first step, the driving signal
is such that the generated twDEP force results in the first and second type of particles
1, 2 moving with a different speed but in a same direction. For example, the first
type of particles 1, e.g. larger particles, may move faster than the second type of
particles 2, e.g. smaller particles, or vice versa. In the example illustrated in
Fig. 2 and Fig. 3, the driving signal is such that first type of particles 1 moves
faster than the second type of particles 2. Hence, upon driving the electrodes 4 of
the first and second regions 5, 6 with a same driving signal, the first and second
type of particles 1, 2 start to move with a different speed in a direction from a
first side of the device to a second side of the device, as indicated with arrows
8 and 9 in Fig. 2. The difference in speed as a result of a same driving signal is
caused by the difference in dielectric properties of the first and second type of
particles 1, 2. Particle types may differ in size, shape and/or composition, which
will lead to different dielectric properties and thus to different dielectrophoretic
responses. As, according to the present example, the first type of particles 1 moves
faster than the second type of particles 2, the first type of particles 1 will, step
by step, be separated from the second type of particles 2. At a certain point in time,
the driving signal to the electrodes 4 of at least one of the first and second region
5, 6 may be changed, i.e. it may be changed in magnitude or sign or may be switched
off. Changing the signal applied to the electrodes 4 of at least one of the first
and second region 5, 6 may also be referred to as resetting of the array 3. This may
be done when a predetermined one of the first and second type of particles 1, 2 has
reached or is expected to have reached, a boundary 7 between the first and second
region 5, 6 (see further). In the example given, according to embodiments of the present
invention, the driving signal to the electrodes 4 of at least one of the first and
second region 5, 6 may be changed when particles 2 of the second type, e.g. the ones
that move slowest under the applied electrical field, have reached or are expected
to have reached the boundary 7 between the first and second region 5, 6.
[0081] The point in time when the driving signal to the electrodes 4 of at least one of
the first and second region 5, 6 is changed may be determined in different ways. Therefore,
the dielectrophoretic device according to embodiments of the present invention can
operate in three modes, i.e. a blind mode, a direct detection mode and an integration
mode.
[0082] In the blind mode, no detection mechanism is present for determining reaching of
one of the first or second type of particles 1, 2, in the example given the second
type of particles 2, of the boundary 7 between the first and second region 5, 6 or
for determining the relative speed of movement of the first and second type of particles
1, 2. A way to ensure separation of at least some of the particles 1 of the first
type from the particles 2 of the second type is by adjusting the time between applying
a same driving signal to all electrodes 4 and changing the driving signal applied
to electrodes 4 of at least one of the first and second region 5, 6, depending on
the required time for the second type of particles 2 to reach the boundary 7 between
the first and second region 5, 6. The time required for the second type of particles
2 to reach the boundary 7 between the first and second region 5, 6 may be determined
from previous experiments, may be simulated, or may be calculated using knowledge
of the DEP response of the first and second type of particles 1, 2, and can then be
chosen so as to be a trade-off between speed of separation and percentage of separation.
[0083] In the case of the blind mode as explained above, changing of the driving signal
to the electrodes 4 of at least one of the first and second region 5, 6 may be done
when at least some of the particles 2 of the second type, e.g. the type of particles
which move slowest under the applied electrical field, are expected to have reached
the boundary 7 between the first and second region 5, 6 based on the experiments,
simulations or calculations performed.
[0084] The blind mode of operation may be advantageous when the dielectrophoretic device
comprises passive arrays and is, for particular reasons, fabricated on a glass substrate,
as this mode of operation requires no integration of electronics in the substrate.
[0085] Another kind of operation mode is the direct mode. In the direct mode, a driving
scheme may be used for the electrodes 4 that requires a feedback process for detecting
crossing of the boundary 7 by a single particle or a group of particles of a particular
type 2 as they move under the DEP forces. For example, a detection means may be present
in the dielectrophoretic device for determining when, in the example given, at least
some of the second type of particles 2 reach the boundary 7 between the first and
second region 5, 6. The most suitable means of detection may be via an optical approach,
i.e. via an optical detector e.g. with integrated PIN diodes. When a particle or group
of particles reduces the level of ambient light falling onto an optical detector,
this change can be used to trigger that a particular amount of the particles 1 of
the first type which move fastest have reached the boundary 7 between the first and
second region 5, 6 and that the signal applied to the electrodes 4 of at least one
of the first and second region 5, 6 may be changed. Whether a particle 1 or 2 has
passed the optical detector may be determined from the Clausius-Mossotti curve in
combination with information obtained from signals detected by the optical detector.
Information obtained from such Clausius-Mossotti curves may reveal the speed difference
of two types of particles 1, 2, so that after a time x, a finite number of particles
1 of the first type will be expected to have crossed the optical detectors. Hence,
from this, it can be approximated how many particles 1 of the first type will have
passed the boundary 7 before particles 2 of the second type will pass the boundary
7. In combination with the measured signal, this information can then be used to determine
the time for resetting the array 3 of electrodes 4, i.e. for changing the driving
signal to electrodes 4 of at least one of the first and second region 5, 6 of the
array 3.
[0086] To operate in the direct mode, the dielectrophoretic device may thus comprise at
least one position detector, e.g. at least one optical detector 10a, 10b, 10c, present
in between two neighbouring electrodes 4 of the second region 6 close to the boundary
7, preferably in a space between the first and second electrode 4 of the second region
6 next to the last electrode 4 of the first region 5 (see Fig. 4). The at least one
optical detector 10a, 10b, 10c may, for example, be a photo diode, as used in Low
Temperature Poly Silicon (LTPS) technology, or may even be a discrete device mounted
on a back of a transparent substrate on which the device is fabricated. According
to embodiments of the invention, the at least one optical detector may comprise discrete
separate detectors 10a, 10b, 10c or may comprise one large sensor located in between
two electrodes 4 of the array 3, preferably located in between two neighbouring electrodes
4 of the second region 6 close to the boundary 7. According to embodiments of the
invention a plurality of detectors 10a, 10b, 10c may be provided such that the whole
length of the space in between two adjacent electrodes 4 is covered, as is illustrated
in Fig. 4.
[0087] In the direct detection mode, changing the driving signal to electrodes 4 of at least
the first or second region 5, 6 may be done upon detection of the predetermined type
of particles, in the example given the second type of particles 2, reaching the boundary
7.
[0088] Fig. 4 illustrates a possible implementation of detection of the predetermined type
of particles, in the example given the second type of particles 2, reaching the boundary
7. Therefore, electronic circuitry may be provided. The electronic circuitry may comprise
a multiplexer switch 13, a reference detector 14, a differential amplifier 15, a detection
unit 16 and a direction control 17. When particles 1 of the first type are crossing
the optical detectors 10a, 10b, 10c, the level of ambient light falling onto these
optical detectors 10a, 10b, 10c will be reduced. A signal representative for this
reduction may then be applied to the differential amplifier 15 where it is compared
with a reference signal, e.g. a signal coming from the reference detector 14. The
signal from the reference detector 14 is representative for ambient light falling
on the reference detector 14 without being reduced, as there are no particles 1 on
this reference detector 14. From this comparison, the level of reduction of the ambient
light by the particles 1 can be determined. The output signal of the amplifier 15
is representative for the level of reduction of the ambient light falling onto the
optical detectors 10a, 10b, 10c and thus for the amount of particles 1 having crossed
the boundary 7. This signal is then sent to the detection unit 16, where, based on
this signal, a determination is made of whether a predetermined amount of particles
1 of the first type have crossed the boundary 7. This predetermined amount may be
set using the speed difference information obtained from the Clausius-Mossotti curves.
The predetermined amount of particles 1 of the fist type may be set to be the amount
of particles 1 which has already passed the boundary 7 at the time that particles
2 of the second type reache the boundary 7. When the detection unit 16 determines
that the determined amount of particles 1 of the first type equals the predetermined
amount, a signal is sent from the detection unit 16 to the direction control 17 which
is connected to a system controller (see further) for resetting the direction control
17, i.e. for changing the driving signal to electrodes 4 of at least one of the first
and second region 5, 6.
[0089] A direct detection of particles 1, 2 may be a secure approach to prevent undesirable
mixing of particles A and B, but detecting a volume of particles which have passed
may be a more efficient marker to use before resetting the array. This is called integration
mode. By using current integration, the surface of the detector 10 covered by particles
will only trigger the reset when a certain volume of first type particles 1 has passed
over the detector 10, also shown in Fig. 4.
[0090] In the integration mode, changing the driving signal to electrodes 4 of at least
the first or second region 5, 6 may be done upon determining that a predetermined
volume of the predetermined type of particles, in the example given the first type
of particles 1, has reached the boundary 7, as detected by the at least one detector
10.
[0091] In the embodiment illustrated in Fig. 4, three detectors 10a, 10b, 10c are present
in between the first and second electrodes 4 of the second region 6. Crossing of the
detectors 10a, 10b, 10c by a particle of the first type 1, is detected by the detectors
10a, 10b, 10c, as discussed hereabove and as illustrated in the right hand side of
Fig. 4 for the 3 different cases illustrated in the left hand side of Fig. 4 (graphs
of current versus time). When a plurality of particles 1 crosses the detectors 10a,
10b, 10c simultaneously, they will obscure more of the ambient light. From Fig. 4
three different situations are illustrated. These three situations are shown by the
current/time plots on the left hand side (first column of graphs) of Fig. 4. In a
first case, only one particle 1 crosses the optical detector 10a and a decrease in
the detected current is recorded. In a second case, two particles 1 cross the optical
detector 10b and there may be a higher decrease in the current. In a third case, two
particles 1 cross the third optical detector 10c slightly overlapping, but, when using
volume detection (see hereinafter), the reduction in integrated current is the same
as in the second optical detector 10b (current x time = charge), this is shown in
the charge/time plots (graphs on the right hand side).
[0092] A volume detection of the crossing of the detectors 10 by the particles is also performed,
as illustrated in the right hand sided of Fig. 4 for the 3 different cases illustrated
in the left hand side of Fig. 4 (graphs of charge versus time). As soon as the volume
detection signal shows that a pre-determined volume of particles have passed the at
least one sensor 10, and hence have passed the boundary 7, according to embodiments
of the present invention, the driving signal to the electrodes 4 of at least one of
the first or second region 5, 6 is changed.
[0093] Changing the driving signal to electrodes 4 of at least one of the first or second
region 5, 6 may be done either by separately addressed electrodes controlled externally
or, if using an Low Temperature Poly Silicon (LTPS) technology, multiplex circuits
can be integrated onto a substrate the electrodes 4 are formed on. Changing of the
signal applied to the electrodes 4 of at least one of the first or second region 5,
6 may, according to embodiments of the invention, be performed in different ways.
For example, the signal applied to the electrodes 4 of the first region 5 may be changed
such that first and second types of particles 1, 2 which have not yet reached the
boundary 7 and thus are still present above the first region 5 move in the opposite
direction as during the first step of the method, i.e. move away from the boundary
7 (indicated by arrow 8 in Fig. 3), while the signal applied to electrodes 4 of the
second region 6 is not changed. Hence, particles 1 of the first type which have already
reached the second region 6, will keep moving in the direction indicated by arrow
9. However, according to other embodiments of the invention, the signal applied to
electrodes 4 of the first region 5 may be switched off while the signal applied to
electrodes 4 of the second region 6 is not changed. In that case, the particles 1,
2 which have not yet reached the boundary 7 between the first and second region 5,
6 may substantially stop moving while particles 1 of the first type will keep moving
in the direction indicated by arrow 9. According to still other embodiments, the signal
applied to electrodes 4 of the second region 6 may also be changed. For example, the
signal applied to the electrodes 4 of the second region 6 may be increased so as to
speed up the movement of the first type of particles 1 in the direction indicated
by reference number 9. Also other driving schemes for driving the electrodes 4 of
the first region 5 and second region 6 may be implemented without departing from the
teaching of the present invention as defined by the appended claims, the driving scheme
being so as to separate at least some particles 1 of the first type from the particles
2 of the second type.
[0094] In the example given in Fig. 2 and Fig. 3, the first type of particles 1 will first
arrive at and cross the boundary 7 between the first and second region 5, 6. After
a particular time period, depending on the difference in dielectric properties between
the first and second type of particles 1, 2, the second type of particles 2 will also
reach the boundary 7. According to the present example, reaching the boundary 7 of
at least one of the particles 2 of the second type may be optically detected (detector
not shown in the figures), as described above. At the moment that at least one of
the particles 2 of the second type reaches the boundary 7 (see Fig. 3), the driving
signal to the electrodes 4 of the first region 5 is changed such that the direction
of movement of the particles 1, 2 which have not yet reached the boundary 7, and which
are thus still present above the first region 5 of the array 3 of electrodes 4, is
changed to the opposite direction (indicated by arrow 8 in Fig. 3).
[0095] In the example given in Fig. 2 and Fig. 3, the driving signal applied to the electrodes
4 of the second region 6 is not changed. The particles 1 of the first type that crossed
the boundary 7 will therefore keep moving (indicated by arrow 9 in Fig. 3) away from
the first region 5 of the array 3. It has to be understood that according to other
embodiments of the invention the driving signal applied to the electrodes 4 of the
second region 6 may also be changed, for example may be increased or enhanced such
that the first type of particles 1 moves faster away from the first region 5.
[0096] Thus, in the embodiment illustrated, any particles 1 that have crossed the boundary
7 between the first and second region 5, 6 will continue to travel in the direction
they were travelling before. These particles 1 may then, for example, be collected
to be detected or to be used for other purposes. For example, they may move towards
a DEP trap 11, where the first type of particles 1 may be held into a confined region,
as illustrated in Fig. 3. According to the present example, the DEP trap 11 may mainly
comprise particles 1 of the first type (once they have been moved to there). In the
example given, the DEP trap 11 may be formed by locating two arrays 3 of electrodes
4 next to each other, such that the second regions 6 of both arrays 3 are adjacent
each other. In between the second regions 6 of the arrays 3, any particle having crossed
the boundary 7, and thus in particular the first type of particles 1 may then be trapped.
[0097] According to embodiments of the invention, detectors may be located in the DEP trap
11 as well. In that case, detection of the trapped particles 1 may be performed. The
detectors may be any type of detectors known by a person skilled in the art.
[0098] Fig. 5 illustrates an example of a distribution of first and second types of particles
1, 2 after a predetermined time of applying a same driving signal to the electrodes
4 of both the first and second region 5, 6 of the array 3. The particles 1, 2 exhibit
a small speed difference. Curve 24 shows the particle distribution for the first type
of particles 1 and curve 25 shows the particle distribution for the second type of
particles 2. The amount of particles 1 of the first type having crossed the boundary
7 between the first and second region 5, 6 is indicated by the dashed area under curve
24.
[0099] According to embodiments of the invention, and as illustrated in Fig. 3, after performing
the above-described steps, there may still be particles 1 of the first type present
between the particles 2 of the second type, or in other words, separation between
the first and second type of particles 1, 2 may not yet be complete. In that case,
the steps as described above may be repeated at least once. Upon repeating these steps
the result may be a high degree of separation between the first and second type of
particles 1, 2 both in location and concentration. The more the steps are repeated,
the higher the degree of separation may be, but the longer the separation time is.
[0100] Fig. 6 illustrates particle distribution curves for three different periods in time
and after different resets. In Fig. 6 curves 24 show particle distribution curves
for the first type of particles 1 and curves 25 show particle distribution curves
for the second type of particles 2. The first column shows the particle distribution
curves 24, 25 during driving the electrodes 4 by applying a same driving signal to
electrodes 4 of both the first and second region 5, 6. In the example given, the first
type of particles 1 moves faster than the second type of particles 2 (distribution
curve 25 is lagging behind with respect to distribution curve 24). Therefore, the
first type of particles 1 will have reached and crossed the boundary 7 between the
first and second region 5, 6 first. The amount of the first type of particles 1 that
has crossed the boundary 7 after a period of 60 seconds is indicated by the dashed
area under curve 24 (lower graph in 1
st column of Fig. 6). It can be seen that after these 60 seconds some of the second
type of particles 2 have also reached the boundary 7. At that moment, the driving
signal may be reset, i.e. the driving signal to electrodes 4 of at least one of the
first and second region 5, 6 may be changed. In the example given, the direction of
the driving signal applied to the electrodes 4 of the first region 5 is switched such
that the particles 1, 2 which have not crossed the boundary 7 go back to their starting
position. Then, a second cycle can be started. This is illustrated in the second column
of Fig. 6. After the return cycle, time is reset as well. At the starting point of
this second cycle, t=0s, the concentration of particles 1 of the first type is lower
than when the experiment started because part of these particles 1 have already crossed
the boundary 7 during the first cycle. Again, first a same signal is applied to electrodes
4 of both the first and second region 5, 6 of the array 3. After another 60 seconds,
another part of the first type of particles 1 have crossed the boundary 7 and some
of the second type of particles 2 may have reached the boundary 7 (see lower graph
of 2
nd column in Fig. 6). At that time, similarly as described above, a reset may be performed
by switching the driving signal applied to the electrodes 4 of the first region 5
such that the particles 1, 2 which have not yet crossed the boundary 7 go back to
their starting position. A third cycle is illustrated in the third column of Fig.
6. After another 60 seconds, another part of the first type of particles 1 has crossed
the boundary 7. It can be seen that in each further cycle, the amount of particles
1 of the first type which have crossed the boundary 7 gets smaller and smaller. This
is because the starting concentration (see first figures in each column) gets lower
and lower as more particles 1 will have crossed the boundary 7 in each further cycle.
[0101] Fig. 7 illustrates the concentration of a first type of particles 1 (curve 26) and
the concentration of a second type of particles 2 (curve 27) that have crossed the
boundary 7 between the first and second region 5, 6 of the array 3 of electrodes 4
as a function of the number of resets. Due to the difference in DEP properties, and
thus in DEP velocities, the concentration of the first type of particles 1 that has
crossed the boundary 7 is higher than the concentration of the second type of particles
2 that has crossed the boundary 7 at a same time. From Fig. 7 it can also be seen,
as was already discussed with respect to Fig. 6, that the higher the number of resets,
the lower the amount of the first type of particles 1 that crosses the boundary 7.
When both types of particles have similar responses, they can still be filtered with
the traditional DEP methods, however they will require proportionally more area (longer
DEP tracks) to filter them apart and they will end up being spread over a much wider
area, both are undesirable as area costs money, and the particle spread then requires
re-focusing. This method ultimately saves space by a factor N in return for N resets.
[0102] The dielectrophoretic device and methods according to embodiments of the invention
may be able to also cope with a mix of different types of particles 1, 2 in a sample
fluid, which have similar dielectric properties. The method according to embodiments
of the invention may only require a more extensive time period between resets in a
blind, direct or integration detection scheme. This may minimise the throughput of
particles 2 of the second type but may also reduce the trapping of undesired particles
1 of the first type in a reservoir adapted for being used with a dielectrophoretic
device according to embodiments of the invention. Such reservoir may be a reservoir,
for example, for collecting particles of the type that moves slowest, this collecting
being performed at the start of the array 3 of electrodes 4, i.e. at the starting
point as referred to above. Alternatively, the reservoir may be a reservoir for, for
example, collecting particles of the type that moves fastest, this collecting then
being performed at the end of the array 3 of electrodes 4, i.e. the side opposite
to the starting point. The reservoir may have an arbitrary shape, for example defined
in a micro fluidic structure with DEP focusing electrodes. The reservoir may be adapted
to pull unidentified particles, i.e. particles of no interest in the experiment, out
of a stream of buffer fluid or sample fluid, and into another reservoir which holds
a similar buffer that may be the same as before, but under no flow conditions or which
is chemically modified to be optimised for the DEP process, i.e. to keep the particles
of no interest in the reservoir. So the desired or undesired particles can be managed
either by moving into a flowing region, or out of a flowing region, or into a different
chemical buffer that alters the DEP behaviour, or performs lysis (e.g. cold water,
making cells swell and burst).
[0103] In addition the flow might be intermittent, the system might perform:
- 1. flow in; 2. filter; 3. flow out process.
[0104] According to alternative embodiments of the present invention, the dielectrophoretic
device may furthermore comprise transport means for transporting trapped particles,
in the example given particles 1 of the first type, towards other regions of the dielectrophoretic
device, or optionally away from the device, so as to enable focusing of selected particles.
This may allow continued particle movement into further regions of the dielectrophoretic
device where they may be used for further reactions or experiments, for example for
cell lysing or for detection. The transport means may, for example, comprise additional
electrodes 12 in a configuration suitable to transport the trapped or collected particles,
in the example given particles 1 of the first type, towards predetermined regions,
e.g. collection regions, of the dielectrophoretic device. An example of a suitable
electrode configuration is illustrated in Fig. 8. In this configuration, additional
electrodes 12 are provided at the end of the second region 6, the additional electrodes
12 being placed in a position perpendicular to the electrodes 4 of the second region
6. The configuration is such that the intersection point of the electrodes 4 of region
6 and the additional electrodes 12 form a diagonal with respect to the configuration
illustrated e.g. in Fig. 3. This configuration allows the particles 1 to move in a
diagonal direction towards a predetermined region, e.g. collection region, of the
dielectrophoretic device, where they can be detected or where experiments or reactions
can take place.
[0105] According to further embodiments of the present invention, the dielectrophoretic
device may comprise a cascade of arrays 3a-3d, each array 3a-3d comprising first and
second regions 5, 6 (see Fig. 9). In the embodiment illustrated in Fig. 9, the cascade
is such that a second zone of a preceding array 3a, 3b, 3c is placed adjacent a first
zone of a subsequent array 3b, 3c, 3d. This may enhance the efficiency of the manipulation
process to a great extent while still maintaining a high throughput of particles 1,
2. Each array 3a-3d of the cascade may be driven one after the other, and in that
way may result in a high degree of separation between the first and second particles
1, 2 present in the sample fluid.
[0106] According to embodiments of the invention, electrodes 4 of the first and second region
5, 6 of the array 3 may be driven with power signals, e.g. voltage signals, adapted
in order to obtain twDEP. In general, generating twDEP requires a phase shift of 360°/n
between neighbouring electrodes 4, with n being higher than 2. For example, n may
be chosen to be 3 or 4. The value of n may kept low because in these cases less different
signals are required and thus simpler electronics may be provided to the dielectrophoretic
device. According to an embodiment of the invention illustrated in Figs. 10 and 11,
n may be 4 and neighbouring electrodes 4 in the array 3 may be energized or driven
with power signals, e.g. voltage signals, with a mutual phase difference of 90° in
order to obtain twDEP, respectively without and with direction control 17.
[0107] The dielectrophoretic device and method according to embodiments of the present invention
may be used to improve results of biological experiments. For example, the dielectrophoretic
device and method according to embodiments of the present invention may be used to
obtain a good efficiency in cell lysing, to improve the obtainable quantity of amplicons
for specific polymer chain reaction (PCR) experiments and improve detection of hybridised
DNA.
[0108] In a further aspect, the present invention also provides a system controller 30 for
use in dielectrophoretic device for controlling driving of the electrodes 4 of an
array 3 in a dielectrophoretic device according to embodiments of the present invention.
The system controller 30, which is schematically illustrated in Fig. 12, comprises
a control unit 31 for controlling a driving means 32 for first driving the electrodes
4 of the first and second region 5, 6 with a same driving signal and subsequently
changing the driving signal to electrodes 4 of at least one of the first and second
region 5, 6. For example, the control unit 31 may be adapted for controlling driving
means 32 for applying a voltage signal to the electrodes 4 with a mutual phase difference
of 360°/n between every two neighbouring electrodes 4, with n being higher than 2.
According to embodiments of the invention, n may be 4 and the system controller 30
may be adapted for controlling driving means 32 for applying a voltage signal to the
electrodes 4 with a mutual phase difference of 90° between every two neighbouring
electrodes 4. The changing of the driving signal may be so as to separate at least
some particles 1 of the first type from the particles 2 of the second type. The system
controller 30 may be adapted for changing the driving signal to electrodes 4 of at
least one of the first and second region 5, 6 upon reaching of the boundary 7 by a
predetermined one of the at least first and second type of particles 1, 2. Therefore,
the system controller 30 may comprise an input port for receiving a detector signal
from a detector 10 detecting reaching of the boundary 7 by a predetermined one of
the at least first and second type of particles 1, 2. According to embodiments of
the invention, and as illustrated in Fig. 4, electronic circuitry may be present in
between the at least one detector 10a, 10b, 10c and the system controller 30.
[0109] The system controller 30 may include a computing device, e.g. microprocessor, for
instance it may be a micro-controller. In particular, it may include a programmable
controller, for instance a programmable digital logic device such as a Programmable
Array Logic (PAL), a Programmable Logic Array, a Programmable Gate Array, especially
a Field Programmable Gate Array (FPGA). The use of an FPGA allows subsequent programming
of the dielectrophoretic device, e.g. by downloading the required settings of the
FPGA. The system controller 30 may be operated in accordance with settable parameters,
such as driving parameters, for example temperature and timing parameters, as well
as amplitude and frequency of the applied electric fields.
[0110] The method described above according to embodiments of the present invention may
be implemented in a processing system 40 such as shown in Fig. 13. Fig. 13 shows one
configuration of processing system 40 that includes at least one programmable processor
41 coupled to a memory subsystem 42 that includes at least one form of memory, e.g.,
RAM, ROM, and so forth. It is to be noted that the processor 41 or processors may
be a general purpose, or a special purpose processor, and may be for inclusion in
a device, e.g., a chip that has other components that perform other functions. Thus,
one or more aspects of the method according to embodiments of the present invention
can be implemented in digital electronic circuitry, or in computer hardware, firmware,
software, or in combinations of them. The processing system may include a storage
subsystem 43 that has at least one disk drive and/or CD-ROM drive and/or DVD drive.
In some implementations, a display system, a keyboard, and a pointing device may be
included as part of a user interface subsystem 44 to provide for a user to manually
input information, such as parameter values. Ports for inputting and outputting data,
e.g. desired or obtained flow rate, also may be included. More elements such as network
connections, interfaces to various devices, and so forth, may be included, but are
not illustrated in Fig. 13. The various elements of the processing system 40 may be
coupled in various ways, including via a bus subsystem 45 shown in Fig. 13 for simplicity
as a single bus, but will be understood to those in the art to include a system of
at least one bus. The memory of the memory subsystem 42 may at some time hold part
or all (in either case shown as 46) of a set of instructions that when executed on
the processing system 40 implement the steps of the method embodiments described herein.
[0111] The present invention also includes a computer program product which provides the
functionality of any of the methods according to the present invention when executed
on a computing device. Such computer program product can be tangibly embodied in a
carrier medium carrying machine-readable code for execution by a programmable processor.
The present invention thus relates to a carrier medium carrying a computer program
product that, when executed on computing means, provides instructions for executing
any of the methods as described above. The term "carrier medium" refers to any medium
that participates in providing instructions to a processor for execution. Such a medium
may take many forms, including but not limited to, non-volatile media, and transmission
media. Non-volatile media includes, for example, optical or magnetic disks, such as
a storage device which is part of mass storage. Common forms of computer readable
media include, a CD-ROM, a DVD, a flexible disk or floppy disk, a tape, a memory chip
or cartridge or any other medium from which a computer can read. Various forms of
computer readable media may be involved in carrying one or more sequences of one or
more instructions to a processor for execution. The computer program product can also
be transmitted via a carrier wave in a network, such as a LAN, a WAN or the Internet.
Transmission media can take the form of acoustic or light waves, such as those generated
during radio wave and infrared data communications. Transmission media include coaxial
cables, copper wire and fibre optics, including the wires that comprise a bus within
a computer.
[0112] It is to be understood that although preferred embodiments, specific constructions
and configurations, as well as materials, have been discussed herein for devices according
to the present invention, various changes or modifications in form and detail may
be made without departing from the scope of this invention as defined by the appended
claims.
1. A dielectrophoretic device for manipulation of at least a first and a second type
of particles (1, 2) present in a sample fluid, the device comprising:
- at least one array (3) of electrodes (4), the array (3) comprising at least a plurality
of electrodes (4) in a first region (5) and a plurality of electrodes (4) in a second
region (6),
- driving means (32) for driving the electrodes (4) of the first and second region
(5, 6) of the array (3) to generate a travelling wave dielectrophoretic force to be
exerted on the at least first and second types of particles (1, 2), and
- a controller (30) for controlling the driving means (32), the controller (30) being
adapted for first driving the electrodes (4) of the first and second region (5, 6)
with a same driving signal and subsequently changing the driving signal to electrodes
(4) of at least one of the first and second region (5, 6) so as to separate at least
some particles (1) of the first type from the particles (2) of the second type.
2. A dielectrophoretic device according to claim 1, there being a boundary (7) between
the first and second region (5, 6), wherein the controller (30) is adapted for changing
the driving signal to electrodes (4) of at least one of the first and second region
(5, 6) upon reaching of the boundary (7) by a predetermined one of the at least first
and second type of particles (1, 2).
3. A dielectrophoretic device according claim 2, furthermore comprising collection means
(11) for collecting at least one of the first and second type of particles (1,2) which
have crossed the boundary (7).
4. A dielectrophoretic device according to claim 3, wherein the collection means (11)
is formed by a dielectrophoretic trap.
5. A dielectrophoretic device according to claim 3 or 4, furthermore comprising transport
means (12) for transporting collected particles (1, 2).
6. A dielectrophoretic device according to any of claims 2 to 5, furthermore comprising
detection means for detecting reaching of the boundary (7) by the predetermined one
of the at least first and second type of particles (1, 2).
7. A dielectrophoretic device according to claim 6, wherein the detection means is an
optical detection means (10).
8. A dielectrophoretic device according to claim 6, wherein the detection means is a
time determination means.
9. A dielectrophoretic device according to claim 6, wherein the detection means is means
for determining a predetermined volume of at least one of the first and second type
of particles (1, 2) which have passed the boundary (7).
10. A dielectrophoretic device according to any of the previous claims, wherein the dielectrophoretic
device comprises a cascade of arrays (3a-3d) of electrodes (4).
11. Use of the dielectrophoretic device according to any of the previous claims for particle
separation or sorting.
12. Method for forming a dielectrophoretic device for manipulation of at least a first
and second type of particles (1, 2) in a sample fluid, the method comprising:
- providing at least one array (3) of electrodes (4), the array (3) comprising at
least a plurality of electrodes (4) in a first region (5) and a plurality of electrodes
(4) in a second region (6),
- providing driving means (32) for driving the electrodes (4) of the first and second
region (5, 6) of the array (3) to generate a travelling wave dielectrophoretic force
to be exerted on the at least first and second types of particles (1, 2), and
- providing a controller (30) for controlling the driving means (32), the controller
(30) being adapted for first driving the electrodes (4) of the first and second region
(5, 6) with a same driving signal and subsequently changing the driving signal to
electrodes (4) of at least one of the first and second region (4, 5) so as to separate
at least some particles (1) of the first type from the particles (2) of the second
type.
13. Method according claim 12, there being a boundary (7) between the first and second
region (5, 6), wherein the method furthermore comprises providing collection means
(11) for collecting at least one of the first and second type of particles (1,2) which
have crossed the boundary (7).
14. Method according to claim 12 or 13, furthermore comprising providing transport means
(12) for transporting collected particles (1, 2).
15. Method according to any of claims 12 to 14, there being a boundary (7) between the
first and second region (5, 6), wherein the method furthermore comprises providing
detection means for detecting reaching of the boundary (7) by a predetermined one
of the at least first and second type of particles (1, 2).
16. Method according to any of claims 12 to 15, wherein providing at least one array (3)
of electrodes (4) is performed by providing a cascade of arrays (3a-3d).
17. Method for manipulating at least a first and second type of particles (1, 2) in a
sample fluid, the method comprising:
a) providing sample fluid comprising the at least first and second type of particles
(1, 2) to a microfluidic device comprising at least one array (3) of electrodes (4),
the array (3) comprising at least a plurality of electrodes (4) in a first region
(5) and a plurality of electrodes (4) in a second region (6),
b) applying a same driving signal to electrodes (4) of the first and second regions
(5, 6), the driving signal being such that the first type of particles (1) and the
second type of particles (2) move with a different speed, and
c) subsequently changing the driving signal to electrodes (4) of at least one of the
first and second regions (5, 6) so as to separate at least some particles (1) of the
first type from the particles (2) of the second type.
18. Method according to claim 17, there being a boundary (7) between the first and second
region (5, 6), wherein the method furthermore comprises, before changing the driving
signal to electrodes (4) of at least one of the first and second region (5, 6), determining
when a predetermined one of the first and second type of particles (1, 2) has reached
the boundary (7).
19. Method according to claim 17 or 18, wherein determining when a predetermined one of
the first and second type of particles (1, 2) has reached the boundary (7) is performed
by an optical detection means (10).
20. Method according to claim 17 or 18, wherein determining when a predetermined one of
the first and second type of particles (1, 2) has reached the boundary (7) is performed
by means of calculating a time period required for the predetermined one of the first
and second type of particles (1, 2) has reached the boundary (7).
21. Method according to any of claims 17 to 20, furthermore comprising repeating steps
b and c at least once.
22. Method according to any of claims 17 to 21, furthermore comprising collecting at least
one of the first and second type of particles (1, 2).
23. Method according to claim 22, furthermore comprising detecting the collected particles
(1, 2).
24. A controller (30) for controlled driving of electrodes (4) of an array (3), the array
(3) comprising at least a plurality of electrodes (4) in a first region (5) and a
plurality of electrodes (4) in a second region (6), wherein the controller (30) comprises
a control unit (31) for controlling a driving means (32) for first driving the electrodes
(4) of the first and second region (5, 6) with a same driving signal and subsequently
changing the driving signal to electrodes (4) of at least one of the first and second
region (5, 6) so as to separate at least some particles (1) of the first type from
the particles (2) of the second type.
25. A controller (30) according to claim 24, there being a boundary (7) between the first
and second region (5, 6), wherein the controller (30) is adapted for changing the
driving signal to electrodes (4) of at least one of the first and second region (5,
6) upon reaching of the boundary (7) by a predetermined one of the at least first
and second type of particles (1, 2).
26. Computer program product for performing, when executed on a computing means, a method
as in any of claims 17 to 23.
27. A machine readable data storage device for storing the computer program product of
claim 26.
28. Transmission of the computer program product of claim 26 over a local or wide area
telecommunications network.