CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
TECHNICAL FIELD
[0002] The present invention relates to an energy conversion system as defined in claim
1.
BACKGROUND
[0003] Electromechanical assemblies based on suspended nanotubes and other molecular-scale
electrically conductive and mechanically flexible wires and their use as motors, generators,
pumps, fans, compressors, propulsion systems, transmitters, receivers, heat engines,
heat pumps, magnetic field sensors, magnetic field generators, inertial energy storage,
and acoustic energy conversion are described in
U.S. Patent No. 7,196,450, issued to Pinkerton et al., on March 27, 2007, entitled "Electromechanical Assemblies Using Molecular-Scale Electrically Conductive
And Mechanically Flexible Beams And Methods For Application Of Same". Heat activated
nanometer-scale pumps are described in
U.S. Patent Application Publication No. 20070048160 to Pinkerton, published March
1, 2007, entitled "Heat Activated Nanometer-Scale Pump".
[0004] Thermally driven excitations of multi-wall carbon nanotubes (MWNTs), clamped at one
end only, were investigated by
Treacy, et al. (Nature 1996, 381, 678). Electrically driven mechanical vibrations of multi-walled nanotubes was observed
by
Poncharal, et al. (Science, 1999, 283, 1513).
Babic, et al. (Nano Letters 2003, 3(11), 1577) later described thermally driven mechanical vibrations of suspended doubly
clamped single-wall carbon nanotubes (SWNTs) in thermal equilibrium at room temperature,
and calculated the Young's modulus of CVD-grown SWNTs from the measured rms vibration
amplitude.
[0005] Document
US 2013/028767 A1 discloses an energy conversion system to convert heat into a flow of fluid by means
of nanofilaments made of graphene. The vibration of the nanofilaments is caused by
thermal energy and can be increased with an electrical input in case a greater flow
of fluid is required. The vanes and the channel of this document are not made of graphene
and a resistor connected electrically with the vanes is not present.
SUMMARY OF THE INVENTION
[0007] The invention relates to a nanomechanical and/or nanoelectromechanical nanofilament
pump assembly apparatuses and methods of use thereof. Such nanomechanical and nanoelectromechanical
nanofilament pump assemblies utilize thermally generated power to create or enhance
fluid flow.
[0008] In an example not falling within the scope of the invention an apparatus includes
a nanomechanical pump assembly, with the nanomechanical pump assembly including (a)
a body having a cavity, (b) nanofilaments, (c) a surface, and (d) a fluid flow path
through the body. The body includes at least two openings, with the first opening
to allow fluid to flow into the cavity, and the second opening to allow the fluid
to flow out of the cavity. The nanofilaments are coupled to the body within the cavity
and are operable to vibrate in response to thermal forces. The surface is proximate
to the nanofilaments. The fluid flow path allows the fluid to flow (i) through the
cavity from the first opening to the second opening, and (ii) by the surface and at
least one of the nanofilaments. The surface and the nanofilaments are positioned within
the cavity such that molecules of the fluid can collide with some (or all) of the
surface and nanofilaments so that the molecules are accelerated along the fluid flow
path due to thermal vibration of the nanofilaments.
[0009] The nanofilaments can include cantilevered nanofilaments.
[0010] The nanofilaments can include carbon nanotubes.
[0011] The nanomechanical pump assembly can further include supports in the cavity. At least
one of the nanofilaments can be coupled to a support at a first location along the
length this first nanofilament. Furthermore, this first nanofilament can also be coupled
to a second support at a second location along the length of this first nanofilament.
[0012] The surface can include pillars. The nanofilaments can be proximate to pillars (
i.e., one nanofilament proximate to one of the pillars, another filament proximate this
pillar or another pillar,
etc.).
[0013] The surface can include a wedge.
[0014] The first opening can include multiple holes in the body through which the fluid
can flow into the body. Some (or all) of these holes are proximate to at least one
nanofilament (
i.e., the first hole is proximate to a nanofilament or a group of nanofilaments, the
second hole is proximate to a different nanofilament or a different group of nanofilaments,
etc.).
[0015] The body can include a channel and vanes. At least some vanes can have positioned
within them at least one nanofilament (
i.e., one vane having a nanofilament or a group of nanofilaments positioned within it,
another vane having a different nanofilament or a different group of nanofilaments
positioned within it,
etc.).
[0016] The nanomechanical pump assembly can be a nanoelectromechanical pump assembly.
[0017] The nanoelectromechanical pump assembly can further include an electrically conductive
surface proximate the nanofilaments, with these nanofilaments operable to be intermittently
electrostatically attracted to the electrically conductive surface such that (a) the
nanofilaments are operable to oscillate in response to the intermittent electrostatic
attraction, and (b) the oscillation of nanofilaments is operable to accelerate the
molecules along the fluid flow path.
[0018] The nanoelectromechanical pump assembly can further include supports in the cavity.
The first nanofilament can be coupled to a first support at a first location along
the length the first nanofilament, and also coupled to a second support at a second
location along the length of the first nanofilament.
[0019] The apparatus can further include a generator. The nanomechanical pump assembly can
be operatively connected to the generator such that the fluid can flow from the nanomechanical
pump assembly to the generator. The generator can also be operable for generating
electricity based upon the flow of fluid from the nanomechanical pump assembly.
[0020] The generator can further include a turbine generator having a fluid intake. The
nanomechanical pump assembly can be operatively connected to the turbine generator
such that the fluid can flow from the nanomechanical pump assembly to the turbine
generator through the fluid intake.
[0021] The apparatus can further include a unit. The unit can be positioned in the apparatus
such that (a) the nanomechanical pump assembly can cool the unit, (b) heat from the
unit can be at least a part of the thermal forces operable to vibrate the nanofilaments,
or (c) both. The unit can be an integrated circuit, a semiconductor device, a microchip,
etc.
[0022] The nanomechanical pump assembly can further include a focusing element. The focusing
element focuses can be positioned to increase the thermal forces that are applied
upon the nanofilaments. The focusing element can further include concave reflective
recesses operable to focus light on the nanofilaments (
i.e., one concave reflective recess is operable to focus light on one nanofilament, another
concave reflective recess is operable to focus light on another nanofilament,
etc.).
[0023] A method of accelerating molecules in a fluid may be as follows: (a) directing a
flow of the fluid toward a nanofilament undergoing thermal vibration and a surface
proximate the nanofilament. This method further includes (b) allowing molecules in
the fluid to collide with the nanofilament and the surface, such that the molecules
are accelerated. This method further includes (c) directing a flow of the accelerated
fluid molecules toward a target.
[0024] The method can further include applying a voltage to an electrically conductive surface
such that the nanofilament oscillates in response.
[0025] In an example not falling within the scope of the invention a nanomechanical pump
includes (a) a body, (b) nanofilaments, and (c) a surface. The nanofilaments include
a free moving portion having a first side. The nanofilaments are coupled to the body,
and the free moving portions of the nanofilaments are operable to exchange kinetic
energy with fluid molecules of a fluid by striking and accelerating the fluid molecules.
The first sides of the free moving portions of the nanofilaments are located proximate
to the surface such that the free moving portions are operable to strike a fraction
of the fluid molecules against the surface before the accelerated fluid molecules
can strike another fluid molecule.
[0026] The fraction can be at least about 10%.
[0027] The fluid can include air.
[0028] The nanofilaments can include carbon nanotubes.
[0029] In an example not falling within the scope of the invention an apparatus includes
(a) an assembly, (b) nanofilaments, and (c) a surface. The nanofilaments are coupled
to the assembly, with the nanofilaments operable to vibrate in response to thermal
forces. The surface is proximate to at least some of the nanofilaments. The surface
and the plurality of nanofilaments are positioned such that molecules of a fluid can
collide with some (or all) of the surface and nanofilaments so that the assembly will
be accelerated in a first direction due to thermal vibration of the nanofilaments.
[0030] The apparatus can further include (d) a rotating support and (e) a generator. The
rotating support can support the assembly and is operable for rotating in the first
direction. The generator can be operable to generate electricity due to the rotation
of the rotating support.
[0031] In an example not falling within the scope of the invention an apparatus includes
a pump assembly, with the pump assembly including (a) a plate having an opening having
an edge, and (b) cantilevered molecular-scale beams positioned over the opening. The
cantilevered molecular-scale beams each have a tip that is proximate the edge of the
opening. The cantilevered molecular-scale beams are operable to asymmetrically oscillate
such that molecules of a fluid are accelerated through the opening.
[0032] The plate can include a second opening having an edge. The pump assembly can further
include additional cantilevered molecular-scale beams positioned over the second opening.
The additional cantilevered molecular-scale beams each have a tip that are proximate
the edge of the second opening. The additional cantilevered molecular-scale beams
are operable to asymmetrically oscillate such that molecules of the fluid are accelerated
through the second opening.
[0033] The cantilevered molecular-scale beams can include cantilevered nanofilaments. The
additional cantilevered molecular-scale beams can also include cantilevered nanofilaments.
[0034] The cantilevered molecular-scale beams can include cantilevered carbon nanotubes.
The additional cantilevered molecular-scale beams can also include cantilevered carbon
nanotubes.
[0035] In an example not falling within the scope of the invention an apparatus includes
a pump assembly, with the pump assembly including (a) a first surface, (b) a second
surface, (c) an opening, and (d) cantilevered molecular-scale beams. The second surface
is linearly spaced from the first surface. The cantilevered molecular-scale beams
are coupled to the first surface at their first ends (
i.e., a first cantilevered molecular-scale beams is coupled to the first surface at its
first end, a second cantilevered molecular-scale beams is coupled to the first surface
at its first end,
etc.). The other ends of the cantilevered molecular-scale beams are free ends proximate
the second surface (
i.e., the other end of the first cantilevered molecular-scale beams is a free end proximate
the second surface, the other end of the second cantilevered molecular-scale beams
is a free end proximate the second surface,
etc.). Some of the free ends are proximate an edge of the second surface, while some
of the free ends are not proximate the edge of the second surface (for example, the
free end of the first cantilevered molecular-scale beams is proximate the edge of
the second surface, while the free end of the second cantilevered molecular-scale
beams is not). The cantilevered molecular-scale beams are operable for accelerating
molecules of a fluid through the opening by asymmetric oscillation of the cantilevered
molecular-scale beams.
[0036] The apparatus can further include a generator operatively connected to the pump assembly.
[0037] The apparatus can further include a unit operatively connected to the pump assembly.
The unit can be an integrated circuit, a semiconductor device, a microchip,
etc.
[0038] A method of accelerating molecules in a fluid may be as follows:
- (a) directing a flow of the fluid toward a asymmetrically oscillating molecular-scale
beams. The method further includes (b) allowing molecules in the fluid to collide
with the beams such that the molecules are accelerated away from the beams.
[0039] In an example not falling within the scope of the invention a nanomechanical pump
includes
- (a) a body, (b) cantilevered nanofilaments, and (c) a surface. The cantilevered nanofilaments
are coupled to the body and include a free moving portion (i.e., a first cantilevered nanofilaments is coupled to the body and has a free moving
portion, a second cantilevered nanofilaments is coupled to the body and has a free
moving portion, etc.). The free moving portions of the cantilevered nanofilaments are operable to exchange
kinetic energy with a plurality of fluid molecules of a fluid by striking the fluid
molecules. The surface is substantially perpendicular to the cantilevered nanofilaments.
The surface is located a distance from the free moving portions of the cantilevered
nanofilaments. The surface has an edge near some of the free moving portions that
is operable to restrict their motion through a non-contact force.
[0040] The non-contact force can include a van der Waals force.
[0041] The non-contact force can include an electrical force.
[0042] The distance can be at most about one nanometer.
[0043] The fluid can include air.
[0044] The cantilevered nanofilaments can include cantilevered carbon nanotubes.
[0045] According to the invention, an energy conversion system including an energy conversion
device as defined in claim 1 is provided. The energy conversion device includes a
first graphene vane, a second graphene vane, a graphene channel, and a resistor having
a first terminal and a second terminal. The first graphene vane is electrically connected
to the graphene channel at a first angle. The second graphene vane is electrically
connected to the graphene channel at a second angle. The first terminal is electrically
connected to the first graphene vane. The second terminal is electrically connected
to the second graphene vane.
[0046] Implementations of the invention can include one or more of the following features:
[0047] The first angle can be between 10 degrees and 80 degrees relative to the graphene
channel. The second angle can be between 10 degrees and 80 degrees relative to the
graphene channel.
[0048] The first angle can be between 20 degrees and 40 degrees relative to the graphene
channel. The second angle can be between 20 degrees and 40 degrees relative to the
graphene channel.
[0049] The energy conversion system can include an array of a plurality of the energy conversion
devices in series.
[0050] Average series voltage can be approximately at most 4 volts.
[0051] The energy conversion system can include an array of a plurality of the energy conversion
devices in parallel.
[0052] Average parallel voltage can be approximately at most 4 volts.
[0053] The parallel array can be comprised of a plurality of layers in which each of the
layers can include an energy conversion device of the energy conversion devices.
[0054] The energy conversion system can further include a substrate adjacent to the graphene
channel.
[0055] The substrate can include hexagonal boron nitride.
[0056] The energy conversion system can include an array of a plurality of energy conversion
devices in parallel.
[0057] The array can include a plurality of layers.
[0058] The layers of the plurality of layers can include a graphene layer and hexagonal
boron nitride layer for the energy conversion device in the plurality of energy conversion
devices.
[0059] The layers in the energy conversion device in the plurality of energy conversion
devices can include a bottom layer of hexagonal boron nitride, a middle layer of graphene,
and an upper layer of hexagonal boron nitride, in which, for at least some adjacent
energy conversion devices in the plurality of energy conversion devices, the bottom
layer of hexagonal boron nitride of an upper adjacent energy conversion device is
the upper layer of hexagonal boron nitride for a bottom adjacent energy conversion
device.
[0060] Mean free path of an electrical charge within the graphene can be between 0.1 and
10 times of length of the first graphene vane.
[0061] Mean free path of an electrical charge within the graphene is equal to length of
the first graphene vane.
[0062] The energy conversion system can include an array of a plurality of the energy conversion
devices in series and parallel.
[0063] In general, in another aspect, the invention features a device comprising an energy
conversion system having an array of a plurality of the energy conversion devices
in series and parallel. The device is a smart-phone or a smart-watch.
[0064] In an example not falling within the scope of the invention an energy conversion
system includes a vane having a length, a channel, a hole in the vane; and a plurality
of gas molecules. The vane is mechanically connected to the channel at an angle. Mean
free path of the gas molecules is between 0.1 and 10 times the length of the vane.
[0065] The mean free path of the gas molecules can be equal to the length of the vane.
[0066] The angle can be between 10 degrees and 80 degrees.
[0067] The angle can be between 20 degrees and 40 degrees.
[0068] In general, in another aspect, the invention features an energy conversion system
including a sheet of graphene, a channel, a vane, a mean free path and a charge. The
charge is operable to travel a distance down the vane toward the channel. The distance
is approximately equal to the mean free path.
[0069] In this respect, before explaining at least one embodiment of the invention in detail,
it is to be understood that the invention is not limited in its application to the
details of construction and to the arrangements of the components set forth in the
following description or illustrated in the drawings.
DESCRIPTION OF DRAWINGS
[0070] The following drawings form part of the present specification and are included to
further demonstrate certain aspects of the present disclosure. The disclosure may
be better understood by reference to one or more of these drawings in combination
with the detailed description of specific embodiments presented herein.
FIG. 1 depicts pump power per unit area calculated as a function of SWNT length for a SWNT
pump assembly.
FIGS. 2A-2E depict various views of a closed-top heat pump pillar assembly
FIGS. 3A-3C depict various views of an open-top heat pump pillar assembly.
FIGS. 4A-4B depict views of a heat pump wedge assembly.
FIGS. 5A -5B depict views of a closed-top heat pump channel assembly.
FIG. 5C depicts a view of a gas ballistic rectifier assembly.
FIG. 5D depicts a view of an electrical ballistic rectifier assembly.
FIGS. 6A-6B depict views of an open-top heat pump channel assembly.
FIGS. 7A-7D depict various views of a charge pump pillar assembly.
FIGS. 8A-8C depict various views of a charge pump jump rope assembly.
FIGS. 9A-9B depict views of a charge pump channel assembly.
FIG. 10A-C depict apparatuses in which a nanofilament pump assembly is coupled, respectively,
to a (A) an electrical generator, (B) a turbine generator, and (C) an integrated circuit.
FIGS. 11A-11C depict various views of a nanofilament heat pump jump rope assembly with light focusing
capability.
FIGS. 12A-12B depict two views of a pump assembly with van der Waals interactions.
FIGS. 13A-13C depict views of a pump assembly with molecular-scale beams aligned on a conductive
plate.
FIGS. 14A-14C is a cross-sectional view of a nanofilament proximate a window, as shown in FIGS. 13A-13C.
FIGS. 15A-15E depict views of a pump assembly with planar molecular-scale beams.
DETAILED DESCRIPTION
[0071] Nanofilaments can function as nanomechanical resonators that oscillate at high frequencies
with small vibration amplitudes. As used herein, "nanofilament" generally refers to
nanoscale wires or tubes, such as single-wall carbon nanotubes (SWNTs), thin strips
of graphene, zinc oxide nanowires,
etc. For example, SWNTs, with a high Young's modulus and low specific weight, can be incorporated
in nanomechanical and nanoelectrical mechanical pump assemblies that channel the mechanical
vibration modes to provide increased fluid flow in a desired direction. Swept volume
and mass flow for these assemblies can be calculated as described below.
[0072] A nanofilament is modeled as a beam with a given length, radius, and Young's modulus,
and mass and resonant frequency of the nanofilament can be calculated at a desired
temperature (for example, room temperature). With an average number of nanofilaments
per unit area, the average amplitude of thermal vibration and swept volume due to
heat alone or with electrical input can be calculated. Tip velocity due to heat and
electrical input, as well as mass flow of the electrical pump, pump power, and thrust
per unit area and volume, can be calculated to yield thrust per watt, as well as swept
volume and mass flow for a device with a given volume.
[0073] For 3.333 x 10
11 SWNT per cm
2 (radius 0.5 x 10
-9 m, length 30 nm) at a temperature of 300K, the resonant frequency is 1.784 x 10
10 Hz, and an average amplitude of thermal vibration is 1.089 x 10
-10 m. The swept volume due to heat alone is 0.08 ft
3/min, with a tip velocity of 7.77 m/s. The amplitude of electrically powered vibrations
is 1.5 x 10
-9 m. The swept volume due to electrical input is 1.134 ft
3/min, and the tip velocity due to electrical input is 107.026 m/s. The mass flow of
the pump due to heat alone per square centimeter is 4.662 x 10
-5 kg/s, the pump power per cm
2 is 1.408 x 10
-3 W, and the thrust due to the flow of air per cm
2 is 3.623 x 10
-4 N. Per cm
3, the amount of heat required to power the pump is 2.815 x 10
3 W and the thrust due to flow of air is 724.552 N, giving a thrust per watt (N/watt)
of 0.257 s/m. Thus, the swept volume and mass flow for a 1 cm
3 device are 77.704 m
3/s and 93.245 kg/s, respectively. For this system, 3.811 x 10
3 W of heat would be required to lift a 100 kg load.
FIG. 1 depicts the thermal power required to activate the pump per cm
3 calculated as a function of SWNT length.
[0074] The following nanomechanical and nanoelectromechanical nanofilament pump assemblies
demonstrate the use of this thermally generated power to create or enhance fluid flow.
Heat can be supplied by, for example, an ambient environment, the sun, a hot microchip,
burning fuel,
etc. The fluid flow can be converted to other forms of energy such as, for example, mechanical
energy or electricity, with output increasing with increased thermal and/or electrical
input. An array of nanofilament pump assemblies can also be used to convert heat or
electricity into thrust to accelerate and control a vehicle such as an automobile
or an aircraft.
[0075] FIG. 2A depicts heat pump pillar assembly
200 (an embodiment of the present invention). Heat pump pillar assembly
200 includes body
202 with cavity
204, pillars
206, and cantilevered nanofilaments
208 coupled to the body proximate the pillars. Fluid
210 enters the assembly
200 through opening
212 and is pumped through assembly
200 and out opening
214. The pumping action is due to the thermal motion of nanofilaments
208 resulting from interaction between the fluid molecules (
e.g., gas or liquid molecules) with the nanofilaments and also by the thermal motion
of the molecules within the nanofilaments. As there are no openings at the top of
heat pump pillar assembly
200, it is a closed-top heat pump pillar assembly.
[0076] FIG. 2B depicts a top view of the closed-top heat pump pillar assembly
200 with pillars
206 and nanofilaments
208 in cavity
204. Motion of the cantilevered nanofilament
208 is depicted as trace
216 indicating tip displacement of the nanofilament due to thermal vibration. While the
trace
216 is illustrated in
FIG 2B with the nanofilament
218 vibrating in a direction normal to pillar
206, there is nothing to requires the vibration of nanofilament
218 occur only in that direction, and it is not required that nanofilament
208 be limited or restricted to vibrate in such direction.
[0077] FIG. 2C depicts a cross-sectional view inside assembly
200 along segment AA of
FIG. 2B. As shown in
FIG. 2C, fluid molecules
218 collide directly with nanofilament
208 and/or pillar
206. (In
FIG. 2C, nanofilament
208 is illustrated in three vibrational positions; the middle of these three positions
is the equilibrium (vertical) position). Deflection of the nanofilament
208 caused by the collisions are depicted by the range of movement of the nanofilament
away from its equilibrium (vertical) position.
[0078] FIGS. 2D and 2E depict partially cut-away perspective views of assembly
200, with nanofilaments
208 vibrating proximate pillars
206 in cavity
204.
[0079] FIG. 3A depicts heat pump pillar assembly
300 with fluid flow openings
302 in the body
202 of the assembly. (Accordingly, heat pump pillar assembly
300 is an open-top heat pump pillar assembly). As shown in
FIG. 3A, openings
302 are positioned above (
e.g., directly above) the nanofilaments
208. Fluid
210 flows through openings
302 and out opening
214 according to the same mechanism as described for, and illustrated in,
FIGS. 2A-B.
[0080] FIG. 3B depicts a top view of the open-top heat pump pillar assembly
300 with openings
302 and nanofilaments
208 in cavity
204. Motion of the nanofilaments
208 is depicted as trace
216 indicating tip displacement of the nanofilament due to thermal vibration.
[0081] FIG. 3C depicts a cross-sectional view inside assembly
300 along segment DD of
FIG. 3B showing pillar
206 and nanofilament
208 in cavity
204 of the assembly. Fluid molecules
218 enter through opening
302 and collide directly with nanofilament
208 and/or pillar
206. As with the closed-top heat pump pillar assembly shown in
FIG. 2A, in the open-top heat pump pillar assembly
300, deflection of the nanofilament
208 caused by the collisions are depicted by the range of movement of the nanofilament
away from its equilibrium (vertical) position.
[0082] FIG. 4A depicts a cut-away perspective view of heat pump wedge assembly
400 with nanofilaments
208 positioned proximate wedges
402. Fluid molecules
218 collide with wedges
402 and/or nanofilaments
208 and the assembly
400 is accelerated as shown by the arrow
410. The fluid flows in the opposite the direction of movement of the assembly
400. As with the other assemblies described herein, the nanofilaments
208 vibrate in the presence of heat.
[0083] Fluid molecules colliding with the moving tip of nanofilaments
208 are struck as depicted in
FIG. 4B, just as a bat strikes a baseball. As can be seen (and as oriented) in
FIG. 4B, molecules
218 approaching the nanofilament
208 from the right will be hit back toward the right, gaining kinetic energy, while molecules
approaching the nanofilament from the left will be hit back toward the left. Molecules
hit toward the left will hit the incline
404 of wedge
402 and ricochet back toward the nanofilament
208. The distance from the wedge
402 to the nanofilament
208 can be chosen so that the mean free path of air (around 60 nm), is approximately
the same as or greater than the distance from the nanofilament
218 (in its equilibrium (vertical) position) to the incline
404 of wedge
402, so that most of the molecules
218 hitting the incline bounce off the incline and move toward the nanofilament
208. The net effect is fluid molecules
218 are pumped toward the right, and wedge
402 experiences a thrust toward the left, along with a small downward thrust component
(under the orientation of
FIG 4B).
[0084] FIG. 5A depicts an embodiment of a closed-top nanofilament heat pump assembly that accelerates
fluid molecules down a channel. Closed-top heat pump channel assembly
500 has multiple vanes
502, with nanofilaments
208 positioned in the vanes
502. Similar to the embodiment of
FIG. 2A, openings
212 and
214 allow directional flow of fluid
210.
[0085] FIG. 5B depicts a cut-away perspective view of assembly
500, with cantilevered nanofilaments
208 positioned in vanes
502. Vanes
502 are coupled to cavity
204, through which fluid
210 flows from opening
212 to opening
214. Fluid molecules
218 from cavity
204 traveling toward nanofilaments
208 in vanes
502 will typically ricochet back toward the cavity
204, with the accelerated molecules exiting through opening
214.
[0086] FIGS. 5C-5D depict energy conversion systems that employ ballistic rectifier assemblies such
as those described above. A ballistic rectifier can be understood, by a simple concept;
that the materials (gas molecules, electrons, etc.) behave as if they were classical
Newtonian particles. Some materials (such as electrons) can respond to electromagnetic
fields; but the materials otherwise travel in straight paths until they encounter
obstacles, from which they are reflected. An asymmetric structure (such as an asymmetric
angled structure) can deflect the particles and this causes the rectification.
See A. M. Song, "Room-Temperature Ballistic Nanodevices", Encyclopedia of nanoscience
and Nanotechnology, X, 1 (2004).
[0087] FIG. 5C depicts an energy conversion system that employs a gas ballistic rectifier assembly
510. If the mean free path (shown by arrows
511) of the gas molecules
512 (such as nitrogen or oxygen) is between 0.1 and 10 times the path length 1 (such
as indicated
FIG. 5C), the gas molecules
512 entering the holes
513 should move on average in direction
210. Since the mean free path of air at atmospheric pressure is around 60 nm, the path
length should be around 60 nm. By lowering gas pressure it is possible to increase
this path length and allow for larger structures.
[0088] For instance, many structures
510 such as set forth in
FIG. 5C can be arranged in parallel and each feed into a turbine-generator
515 to convert the airflow (generated by heat shown by arrow
514) into an electrical output. The force due to the airflow can also be used directly
to propel a vehicle. In such case, heat
514 is converted into mechanical motion.
[0089] FIG. 5D depicts an energy conversion system that employs an electrical ballistic rectifier
assembly
520. G. Auton et al., "Graphene Ballistic Nano-Rectifier With Very High Responsivity,"
Nature Communications 7, Article number: 11670 (2016) describes how a graphene-based ballistic rectifier operates in general. If the mean
free path 531 of the electron
529 (or other charge carrier) is between 0.1 and 10 times path length 1 (which is similar
to the length of the graphene vane) the electrons
529 entering from the resistor terminals 521 (the resistors
525-528 generate an AC Johnson noise voltage) should move on average in direction
210. Since the mean free path of graphene
524 on top of hexagonal boron nitride (HBN)
523 (which is on top of the substrate
522, such as SiO
2) is around 1000 nm the path length should be around 1000 nm.
[0090] For instance, many structures
520 such as shown in
FIG. 5D can be arranged in series to increase voltage and be placed in parallel to increase
current. Increasing the resistance of resistors
525-528 will increase the output voltage (but not the power output since current will decrease
with increased resistance). An increase power per square centimeter can be obtained
by making many layers of sub strate/HBN/graphene/HBN/sub strate/
etc.
[0091] In energy conversion system using an electrical ballistic rectifier assembly
520, heat (shown by arrow
530) is converted directly into an electrical output without the need for a turbine-generator.
One application can be to convert the heat of a person's wrist/arm into an electrical
output to partially or fully power a smart-watch.
[0092] If one stage (one resistor and two angled legs of graphene/HBN) takes up one square
micrometer, the effective bandwidth of the ballistic rectifier is 1 GHz and each resistor
is 10,000 ohms, a 1 square centimeter array (10,000 stages in series and 10,000 in
parallel) will produce about 1.7 milliwatts at 4 volts (a voltage compatible with
most smartphones). For a 6x10 cm substrate (about the size of a smartphone), the single
layer array should produce about 100 mW (enough to trickle charge a smartphone battery).
If a 10 layer thick array that is 6x10 cm is utilized, the system should produce about
1 watt (enough to power a smartphone indefinitely).
[0093] FIG. 6A depicts an open-top heat pump channel assembly
600 with openings
602 in vanes
502 above (
e.g., directly above) nanofilaments
208. Similar to the embodiment of
FIG. 3A, fluid
210 flows into openings
602. This creates thermal vibrations of nanofilaments
208, and results in movement of the fluid from openings
602 to opening
214.
[0094] FIG. 6B depicts a partially cut-away top view of open-top heat pump channel assembly
600 with nanofilaments
208 in vanes
502 proximate cavity
204.
[0095] Thermal vibrations of the nanofilaments
208 in a nanofilament assembly (such as illustrated in
FIGS. 2A,
3A,
5A,
and 6A) can be augmented with an electrical input. When electrically conductive traces
216 are driven with an AC voltage, the nanofilaments
208 can be made to oscillate as they are intermittently attracted to conductive features
through electrostatic attraction. The resulting vibrational amplitude of the nanofilaments
208 can greatly exceed the vibrational amplitude of nanofilaments
210 in assemblies driven by heat alone.
[0096] The pumping force (or thrust) of a charge pump assembly can be significantly higher
than that of a heat pump assembly. As with heat pump assemblies, the pumping action
of charge pump assemblies is derived from the ricochet action (collisions) of molecules
in the cavity. The electrostatic attraction between the pillar
206 and nanofilament
208 can also be used to adjust the pumping rate due to heat. For example, the fluid flow
due to heat can be slowed by applying a DC voltage between the pillars
206 and nanofilaments
208.
[0097] FIG. 7A depicts a charge pump pillar assembly
700 (closed-top). Charge pump pillar assembly
700 has body
202, cavity
204, and nanofilaments
208 similar to that of heat pump pillar assembly
200 (illustrated in
FIG. 2). Nanofilaments
208 are cantilevered proximate conductive pillars
706. Conductive traces
710 are made of a conductive material such as, for example, copper. Fluid
210 enters the assembly
700 through opening
212 and is pumped through assembly
200 and out opening
214.
[0098] The pumping action is due to the electrostatic attraction of the nanofilaments
208 and the conductive pillars
706, as well as the thermal motion of nanofilaments
208 resulting from interaction between the fluid molecules (
e.g., gas or liquid molecules) with the nanofilaments
208.
[0099] FIG. 7B depicts a cut-away perspective view of the assembly
700 with conductive pillars
706 and nanofilaments
208 in cavity
204.
[0100] As shown in
FIG 7C, motion of the nanofilaments
208 is depicted as trace
216 indicating tip displacement of the nanofilament due to thermal and electrostatic
vibration of the nanofilaments is shown in
FIG. 7C.
[0101] FIG. 7D depicts a cross-sectional view inside assembly
700 along segment AA of
FIG. 7C of conductive pillar
706, nanofilament
208, and conductive trace
710 in cavity
204 of assembly
700. Fluid molecules
218 collide directly with nanofilament
208 and/or conductive pillar
706. Deflection of the nanofilament
208 caused by the collisions are depicted by the range of movement of the nanofilament
208 away from its equilibrium (vertical) position.
[0102] FIG. 8A depicts a charge pump jump rope assembly
800 (closed-top) with body
202, cavity
204, conductive pillars
706, double clamped nanofilaments
808 (shown in
FIG 8B), and conductive traces
710. Nanofilaments
808 are coupled to conductive supports
812, as shown in
FIG. 8B. Fluid
210 flows into cavity
204 through opening
212 and is accelerated out of the cavity through opening
214. The charge pump jump rope assembly
800 functions similarly to the charge pump pillar assembly
700, with the double clamped nanofilaments
808 utilized in place of the cantilevered filaments
208.
[0103] When nanofilaments
808 are SWNTs, the amplitude of vibration can be several times the diameter of the nanofilament
808, even at room temperature in the absence of electrical augmentation. For this embodiment,
SWNTs can be grown in parallel arrays and then transferred to the supports
812 as shown in
FIG. 8B. See, e.g., Cao, et al. (Advanced Materials 2009, 21, 29-53) (including a review of methods to assemble SWNT thin films (Section 2)). There are
benefits for using SWNT in certain embodiments of the present invention because SWNT
are advantageously light, strong, electrically conductive, thermally conductive, and
can withstand very high temperatures.
[0104] FIG. 8C depicts vibrational amplitude of nanofilaments
808 in charge pump jump rope assembly
800. (In
FIG. 8C, nanofilaments
808 are illustrated in three vibrational positions; the middle of these three positions
is the equilibrium (vertical) position).
[0105] FIG. 9A depicts a charge pump channel assembly
900 (closed-top). Charge pump channel assembly
900 functions similarly to heat pump channel assembly
500 (shown in
FIG. 5A), with the addition of conductive traces
710 and a conductive surface
902 on vanes
502. This arrangement creates an intermittent attractive electrostatic force between the
conductive surface
902 and the nanofilaments
208.
[0106] FIG. 9B is a cut-away view of charge pump channel assembly
900 showing nanofilaments
208 attracted toward conductive surface
902 of vanes
502.
[0107] In embodiments of the invention, the nanofilament pump assembly is coupled to a device.
For instance, the pump assembly can be coupled to a device and utilized to generate
electricity
(i.e., the present invention can be utilized for generating electrical power and to convert
solar energy to electrical power).
[0108] FIG. 10A depicts rotating nanofilament pump assembly
1000. Rotating pump assembly
1000 includes a plurality (
e.g., billions) of clamped nanofilaments
808 coupled to supports
1003 on disk
1002, as shown in the inset of
FIG 10. Vibration of the clamped nanofilaments
808 produces torque, which in turn can rotate the disk
1002, resulting in power output from electrical generator
1004. Assembly
1000 can be a heat and/or charge pump assembly (or other assemblies disclosed herein).
[0109] FIG. 10B depicts a stationary nanofilament pump array (such as heat pump pillar assembly
200, as depicted in
FIGS. 2A-2E) operatively coupled to an turbine generator
1010. Other assemblies disclosed herein similarly can be utilized. The stationary nanofilament
pump array creates a fluid flow, and the fluid
210 is fed into the fluid intake
1011 of the turbine generator
1010. The flow of fluid
210 rotates turbine blade
1012, and leaves the turbine generator
1010 at fluid outlet
1013. The rotation of the turbine blade
1012 rotates the main shaft
1014, which in turn spins the coiled wire cylinder
1015 in magnetic field
1016 generating electricity
1017.
[0110] FIG 10C depicts a stationary nanofilament pump array (such as heat pump pillar assembly
200, as depicted in
FIGS. 2A-2E) operatively coupled to an integrated circuit
1020 (such as a CPU). Other assemblies disclosed herein similarly can be utilized. During
normal operation, an integrated circuit can generate a significant amounts of heat.
This heat must be continuously removed, or the integrated circuit may overheat, resulting
in damage to the integrated circuit and/or a reduction in operating performance. Coupling
an integrated circuit (or a semiconductor device, a microchip,
etc.) with a nanofilament pump array allows for its cooling utilizing multiple mechanisms.
[0111] The nanofilament pump array can be positioned such that heat from the integrated
circuit
1020 can be utilized as a source of the thermal force that causes the thermal vibration
of the nanofilaments in the nanofilament pump array. This use of the thermal energy
will act to cool the integrated circuit
1020. The nanofilament pump array can also be positioned such that the fluid flow
210 from the nanofilament pump array will itself cool the integrated circuit
1020 by transporting heat away in the fluid flow.
[0112] FIG. 11A depicts a perspective view of a portion of a heat pump jump rope assembly
1100 with a focusing portion that can be used to focus sunlight on a suspended (clamped)
nanofilament. Nanofilaments
808 are connected to supports
1003 proximate pillars or walls
206. Light (
e.g., sunlight) is focused on the nanofilaments
808 by concave reflective recesses
1102 (or an alternative focusing element) to increase the thermal input to nanofilaments
808. This increases the vibrational amplitude of the nanofilaments
808, resulting in more force/thrust/power from the assembly
1100.
[0113] FIG. 11B depicts a cross-sectional view of a portion of assembly
1100, including nanofilament
808 (vibrational amplitude visible), wall or pillar
206, support
1003, and reflective recess
1102.
[0114] FIG. 11C is magnified cross-sectional view of a portion A of
FIG. 11B. As shown in
FIG 11C, fluid molecules
218 are shown colliding with the wall or pillar
206 and the nanofilament
808.
[0115] In some implementations, the embodiments in
FIGS. 10A and 11A are combined to form a photovoltaic device, such that solar energy is converted to
rotation and then into electrical power.
[0116] The free end of a cantilevered molecular-scale beam or nanofilament (for example,
a carbon nanotube or zinc oxide nanowire) can oscillate with an amplitude approximately
equal to its own diameter based on average thermal energy of the nanofilament at room
temperature. In the absence of other interactions, this thermal motion is symmetrical
over time, such that an array of nanofilaments may not substantially affect the average
flow of a surrounding fluid (gas or liquid). When molecular-scale objects are in close
proximity (
e.g., within a few nanometers of each other), however, dipole-dipole interactions know
as van der Waals (VDW) forces create an attractive force between the objects. For
example, if the tip of a nanofilament is passed within a few nanometers of a sharp
edge, the nanofilament will resist being pulled away from the edge. This effect can
be increased by placing an electric voltage across the nanofilament and edge, such
that opposite electric charges on the nanofilament and the edge increase the attractive
force between the nanofilament and the edge.
[0117] VDW forces (and electrical forces, if present) near an edge can affect the symmetry
of the thermal motion of a nanofilament in close proximity to the edge. Asymmetry
introduced by VDW forces, electrical forces, or a combination thereof, can be designed
such that the thermal motion of some nanofilaments in a pump assembly can be restricted
relative to that of others to create a pumping action.
[0118] As depicted in
FIG. 12A, pump assembly
1200 includes nanofilaments (
1206,
1208, and
1210) coupled to lower trace
1202 (on bottom portion
1214) and positioned beneath upper trace
1204 (below top portion
1212). The nanofilaments
1206 on the left portion of the lower trace
1204 demonstrate limited bending to the left, due, for example to VDW edge effect forces
between the nanofilaments (
1208 and
1210) and the upper trace
1204. In contrast, the nanofilaments
1208 in the middle portion or nanofilaments
1210 in the right portion of the trace are able to oscillate substantially symmetrically
toward the left and right.
[0119] As seen in the cross section of pump assembly
1200 in
FIG. 12B, the tips of nanofilaments
1206 are closer to the edge (in this case, the left edge) of element 1204 (when in an
unbent position) than the tips of nanofilaments
1208 and
1210, positioned toward the center and right of trace
1202, respectively. The thermal motions of the tips of nanofilaments
1206 interact with the edge of
1204 due to VDW forces, but nanofilaments
1208 and
1210 are positioned so that their thermal motions do not interact substantially with an
edge of element
1204.
[0120] The asymmetry in nanofilament motion will tend to pump a fluid from left to right
in the pump assembly shown in
FIGS. 12A and 12B. For example, if a gas molecule traveling at higher than the average velocity from
right to left hits nanofilament
1206, the nanofilament will move slightly to the left before being deflected to the right
by forces, including VDW interactions. Nanofilament
1206 thus bends toward the right and impacts gas molecules (
i.e., the gas molecules collide with the nanofilament), accelerating the molecules toward
the right. After a time, nanofilament will move back toward the left due to the mechanical
spring force of the beam itself. The movement of the nanofilament toward the left
has a lower velocity than the movement of the nanofilament toward the right, such
that the gas molecules hit by the nanofilament moving toward the left accelerate toward
the left at lower rate than the molecules accelerated toward the right. After a few
cycles of nanofilament oscillation, the amplitude of the nanofilament tip motion will
decrease, and asymmetrical pumping action is reduced.
[0121] If a gas molecule traveling at higher than average velocity from left to right hits
a nanofilament with a tip that is located near left edge of elevated trace in
FIGS. 12A and 12B (
e.g., nanofilament
1206), the nanofilament will move to the right before being deflected toward the left
by the mechanical spring force of the nanofilament. The nanofilament may hit gas molecules
while moving toward the right, thereby accelerating these molecules toward the right.
After a time, this nanofilament will move back toward the left (
e.g., due to the mechanical spring force of the nanofilament) at a velocity lower than
that of the movement toward the right, so that the gas molecules hit by the beam accelerate
toward the left at a lower rate than the gas molecules accelerated toward the right.
Nanofilaments closer to the center and the right edge of the lower trace
1202 (
e.g., nanofilaments
1208 and
1210) will experience more symmetrical tip motion and therefore not contribute substantially
to a net pumping action.
[0122] In some embodiments, moving a top portion
1212 of the pump assembly
1210 toward the left or right with respect to the bottom portion
1214 will affect the pumping action. For example, the direction of the pumping action
can be reversed by moving the top portion
1212 to the left relative to the bottom portion
1214.
[0123] FIG. 13A depicts pump assembly
1300 in which a parallel array
1302 of conductive nanofilaments
1304, windows
1306, and conductive plates
1308 and
1310 are arranged to achieve a controllable pumping action. Each of the cantilevered nanofilaments
1304 has a free (
e.g., unattached) tip
1312 that is closer to the top edge
1314 of the window
1306 than the bottom edge
1316 of the window
1306. When the nanofilaments
1304 vibrate with heat or are struck with fluid molecules of above average velocity, the
tips
1312 can move down into the middle of the window
1306 (
e.g., between conductive plates
1308 and
1310). VDW forces inhibit the tips
1312 from moving substantially above the window
1306.
[0124] Pump assembly
1300 allows asymmetrical oscillation of nanofilaments
1304. The asymmetrical oscillation will tend to pump surrounding fluid molecules down through
the window
1306 and create an upward thrust from conductive plate
1310 toward conductive plate
1308.
[0125] As depicted in
FIG 13B, when a DC voltage of sufficient magnitude is placed across the two conductive plates
1308 and
1310, nanofilament
1304 (which is in electrical contact with conductive plate
1308) will deflect through window
1306, due to electrostatic forces between the nanofilaments
1304 and the conductive plate
1310 (or bottom electrode). The DC voltage alters the movement of the nanofilaments
1304, and thus alters the pumping action. The DC voltage across conductive plates
1308 and
1310 can be selected to increase, decrease, reverse, or substantially stop pump flow.
[0126] FIG. 13C is a bottom perspective view, showing conductive plate
1310, with nanofilaments
1304 (and nanofilament tips
1312) visible through windows
1306.
[0127] FIGS. 14A-14C show an enlarged view of nanofilament
1304 positioned on conductive plate
1308 above window
1306, as shown in
FIGS. 13A-13C. Conductive plate
1308 is spaced apart from conductive plate
1310 by distance
d. As seen in
FIG. 14A, with no voltage across conductive plates
1308 and
1310, nanofilament
1304 is substantially parallel to the conductive plates and above window
1306.
[0128] As shown in
FIG. 14B, when voltage is applied across conductive plates
1308 and
1310, nanofilament
1304 moves into window
1306 toward oppositely charged conductive plate
1310.
[0129] FIG. 14C shows nanofilament
1304 substantially fully deflected through window
1306 toward conductive plate
1310. When the potential between conductive plates
1308 and
1310 is reduced or substantially eliminated, nanofilament
1304 will move back toward the parallel position shown in
FIG. 14A.
[0130] The pump assembly in
FIGS. 13A-13C can be made in the following manner. Conventional lithography, etching,
etc., can be used to form the windows
1306 in conductive plates
1308 and
1310 out of silicon or other suitable material. A thin coating of electrically conductive
material can be applied (
e.g., sputtered) on the top and bottom surface of conductive plates
1308 and
1310. Single wall carbon nanotubes (or another type of molecular-scale beam or nanofilament)
can be applied to the top face of the window structure
1306 (
e.g., using transfer printing, the application of a solution including nanotubes, or
other suitable method). The tips
1312 of the nanofilaments
1304 can be cut near the top window edge
1314 by a using a stamp cutter or other method. In some embodiments, the gap between the
nanofilament tip
1312 and the top window edge
1314 is in the range of about 0.1 nm to about 10 nm, or about 1 nm.
[0131] In some embodiments, molecular-scale beams for pump assemblies are cylindrical or
otherwise curved. In other embodiments, molecular-scale beams for pump assemblies
are not intentionally curved (
e.g., substantially rectangular, planar,
etc.), and can include sheets or flakes of a thin material (
e.g., graphene).
[0132] FIGS. 15A-15E depict fabrication and operation of pump assembly
1500 with planar molecular-scale beams.
[0133] As shown in
FIG. 15A, openings
1502 can be cut or carved out of a material (
e.g., silicon) to form an upper plate
1504. As shown in
FIG. 15B, a strip or sheet
1506 (
e.g., a graphene sheet) is applied over the top of openings
1502 on upper plate
1504. Lithography can be used to define the strips
1506 as desired, and the strips can be cut (
e.g., with a punch) near one side of the opening
1502 to form edge
1508, as shown in
FIG. 15C. Edge
1508 is proximate protrusion
1510 on lower plate
1512. FIGS. 15D-15E depict a cross-sectional view of oscillation of beam
1506 proximate opening
1502. (
FIG 15E depicts a cross-sectional view along segment BB of
FIG. 15D).
[0134] Thermal oscillations caused by collision of molecules are shown to create a larger
downward movement into opening
1502 than above the opening. This asymmetrical motion will tend to pump fluid molecules
down through opening
1502 and create an upward thrust on the pump assembly (
e.g., on the conductive plate
1504).
[0135] A number of embodiments of the invention have been described. Nevertheless, it will
be understood that various modifications may be made without departing from the scope
of the invention as defined in the appended claims.
[0136] The embodiments described and the examples provided herein are exemplary only, and
are not intended to be limiting. Many variations and modifications of the invention
disclosed herein are possible and are within the scope of the invention as defined
in the appended claims. For example, nanofilament pump assemblies can be layered or
stacked (for instance, vertically) to increase output. In some embodiments, a sheet
with nanofilament pump assemblies is rolled into a cylinder, and fluid is allowed
to flow from a first end of the cylinder to a second end of the cylinder. Accordingly,
other embodiments are within the scope of the following claims. The scope of protection
is not limited by the description set out above, but is only limited by the claims
which follow.