TECHNICAL FIELD
The present invention relates to an electrically conductive membrane pump/transducer. The electrically conductive pump transducer includes an array of electrically conductive membrane pumps that combine to move a larger membrane (such as a membrane of PDMS). The electrically conductive membranes in the array can be, for example, graphene-polymer membranes.
BACKGROUND
Conventional audio speakers compress/heat and rarify/cool air (thus creating sound waves) using mechanical motion of a cone-shaped membrane at the same frequency as the audio frequency. Most cone speakers convert less than 10% of their electrical input energy into audio energy. These speakers are also bulky in part because large enclosures are used to muffle the sound radiating from the backside of the cone (which is out of phase with the front-facing audio waves). Cone speakers also depend on mechanical resonance; a large “woofer” speaker does not efficiently produce high frequency sounds, and a small “tweeter” speaker does not efficiently produce low frequency sounds.
Thermoacoustic (TA) speakers use heating elements to periodically heat air to produce sound waves. TA speakers do not need large enclosures or depend on mechanical resonance like cone speakers. However, TA speakers are terribly inefficient, converting well under 1% of their electrical input into audio waves.
The present invention relates to an improved transducer (i.e., speaker) that includes an electrically conductive membrane such as, for example, a graphene membrane. In some embodiments, the transducer can be an ultrasonic transducer. An ultrasonic transducer is a device that converts energy into ultrasound (sound waves above the normal range of human hearing). Examples of ultrasound transducers include a piezoelectric transducers that convert electrical energy into sound. Piezoelectric crystals have the property of changing size when a voltage is applied, thus applying an alternating current (AC) across them causes them to oscillate at very high frequencies, thereby producing very high frequency sound waves.
The location at which a transducer focuses the sound can be determined by the active transducer area and shape, the ultrasound frequency, and the sound velocity of the propagation medium. The medium upon which the sound waves are carries can be any gas or liquid (such as air or water, respectively).
Graphene membranes (also otherwise referred to as “graphene drums”) have been manufactured using a process such as disclosed in Lee et al. Science, 2008, 321, 385-388. PCT Patent Appl. No. PCT/US09/59266 (Pinkerton) (the “PCT US09/59266 Application”) described tunneling current switch assemblies having graphene drums (with graphene drums generally having a diameter between about 500 nm and about 1500 nm). PCT Patent Appl. No. PCT/US11/55167 (Pinkerton et al.) and PCT Patent Appl. No. PCT/US11/66497 (Everett et al.) further describe switch assemblies having graphene drums. PCT Patent Appl. No. PCT/US11/23618 (Pinkerton) (the “PCT US11/23618 Application”) described a graphene-drum pump and engine system.
In embodiments of such graphene-drum pump and engine systems the graphene drum could be between about 500 nm and about 1500 nm in diameter (i.e., around one micron in diameter), such that millions of graphene-drum pumps could fit on one square centimeter of a graphene-drum pump system or graphene-drum engine system. In other embodiments, the graphene drum could be between about 10 μm to about 20 μm in diameter and have a maximum deflection between about 1 μm to about 3 μm (i.e., a maximum deflection that is about 10% of the diameter of the graphene drum). As used herein, “deflection” of the graphene drum is measured relative to the non-deflected graphene drum (i.e., the deflection of a non-deflected graphene drum is zero).
FIG. 1 depicts a perspective view of the graphene-drum pump system illustrated in the PCT US11/23618 Application (described in paragraphs [00102]-[00113] and in FIGS. 1-3, therein). FIGS. 2-3 depict close-ups of the graphene-drum pump (in the graphene-drum pump system of FIG. 1) in exhaust mode and intake mode, respectively.
As illustrated in FIGS. 1-3 (which are similar to FIGS. 1-3 of the PCT US11/23618 Application), the top layer 102 is graphene. The top layer is mounted on an insulating material 103 (such as silicon dioxide). Graphene-drum pump 101 utilizes a graphene drum as the main diaphragm (main diaphragm graphene drum 201). The main diaphragm seals a boundary of the cavity 202 of the graphene-drum pump 101. The cavity is also bounded by insulating material 103 and a metallic gate 203 (which is a metal such as tungsten). The metallic gate 203 is operatively connected to a voltage source (not shown), such as by a metallic trace 204. The main diaphragm graphene drum 201 can be designed to operate in a manner similar to the graphene drums taught and described in the PCT US09/59266 Application and PCT US11/23618 Application.
The graphene-drum pump also includes an upstream valve 205 and a downstream valve 206. As illustrated in FIG. 2, upstream valve 205 includes another graphene drum (the upstream valve graphene drum 207). The upstream valve 205 is connected (a) to a fluid source (not shown) by a conduit 208 and (b) to the cavity 202 by conduit 209, which conduits 208 and 209 are operable to allow fluid (such as a gas or a liquid) to flow from the fluid source through the upstream valve 205 and into the cavity 202. The upstream valve 205 also has a cavity 210 bounded (and sealed) by the upstream valve graphene drum 207, the insulating material 103, and upstream valve gate 211. The upstream valve graphene drum 207 can be designed to operate in a manner similar to the graphene drums taught and described in the PCT US09/59266 Application and PCT US11/23618 Application. For instance, the upstream valve 205 can be closed or opened by varying the voltage between upstream valve graphene drum 207 and upstream valve gate 211. When the upstream valve 205 is closed, van der Waals forces will maintain the upstream valve graphene drum 207 in the seated position, which will keep the upstream valve 205 in the closed position.
As illustrated in FIG. 2, the downstream valve 206 includes another graphene drum (the downstream valve graphene drum 212). The downstream valve 206 is connected (a) to the cavity 202 by a conduit 213 and (b) to a fluid output (not shown) by conduit 214, which conduits 213 and 214 are operable to allow fluid to flow from the cavity 202 through the downstream valve 205 and into the fluid output. The downstream valve 206 also has a cavity 215 bounded (and sealed) by the downstream valve graphene drum 212, the insulating material 103, and downstream valve gate 216. The downstream valve graphene drum 212 can be designed to operate in a manner similar to the graphene drums taught and described in the PCT US09/59266 Application and PCT US11/23618 Application. For instance, the downstream valve 206 can be closed or opened by varying the voltage between downstream valve graphene drum 212 and downstream valve gate 216. When the downstream valve 206 is closed, van der Waals forces will maintain the downstream valve graphene drum 212 in the seated position, which will keep the downstream valve 206 in the closed position. Generally, upstream valve gate 211 and downstream valve gate 216 are synchronized so that when the upstream valve 205 is opened, downstream valve is closed (and vice versa).
FIG. 2 depicts the graphene-drum pump 101 in exhaust mode. In the exhaust mode, the upstream valve 205 is closed and the downstream valve 206 is opened, while the main diaphragm graphene drum 201 is being pulled downward (such as due to a voltage between the main diaphragm graphene drum 201 and metallic gate 203). This results in the fluid (such as air) being pumped from the cavity 202 through the downstream valve 205 and into the fluid output.
FIG. 3 depicts graphene-drum pump 101 in intake mode. In the intake mode, the upstream valve 205 is opened and the downstream valve 206 is closed, while the main diaphragm graphene drum 201 moves upward. (For instance, by reducing the voltage between the main diaphragm graphene drum 201 and metallic gate 203, the graphene drum 201 will spring upward beyond its “relaxed” position). This results in the fluid (such as air) being drawn from the fluid source through the upstream valve 205 and into the cavity 202.
To reduce or avoid wear of the upstream valve 205 that utilizes an upstream valve graphene drum 207, embodiments of the invention can include an upstream valve element 217 to sense the position between the upstream valve graphene drum 207 and bottom of cavity 210. Likewise to reduce or avoid wear of the downstream valve 206 that utilizes a downstream valve graphene drum 212, embodiments of the invention can include an downstream valve element 218 to sense the position between the downstream valve graphene drum 212 and bottom of cavity 215. The reason for this is because of the wear that upstream valve 205 and downstream valve 206 will incur during cyclic operation, which can be on the order of 100 trillion cycles during the device lifetime. Because of such wear, upstream valve graphene drum 207 and downstream valve graphene drum 212 cannot repeatedly hit down upon the channel openings to conduit 209 and conduit 213, respectively.
As shown in FIG. 2, upstream valve element 217 is shown in the center/bottom of cavity 210 of the upper valve 205, and downstream valve element 218 is shown in the center/bottom of cavity 215 of downstream valve 206. Upstream valve element 217 is used to sense the position of the upstream valve graphene drum 207 relative to the bottom of cavity 210 by using extremely sensitive tunneling currents as feedback. A separate circuit (not shown) is connected between the upstream valve element 217 and the upstream valve graphene drum 207. Likewise downstream valve element 218 is used to sense the position of the downstream valve graphene drum 207 relative to the bottom of cavity 215 by using extremely sensitive tunneling currents as feedback. A separate circuit (not shown) is connected between the upstream valve element 218 and the upstream valve graphene drum 212.
With respect to the upstream valve 205, when the upstream valve graphene drum 207 is within about 1 nm of the upstream valve element 217, a significant tunneling current will flow between the upstream valve graphene drum 205 and the upstream valve element 217. This current can be used as feedback to control the voltage of upstream valve gate 211. When this current is too high, the gate voltage of upstream valve gate 211 will be decreased. And, when this current is too low, the gate voltage of upstream valve gate 211 will be increased (so that the valve stays in its “closed” position, as shown in FIG. 2, until it is instructed to open). There will likely be a gap (around 0.5 nm) between the upstream valve graphene drum 207 and channel opening to conduit 209 when the upstream valve 205 is closed; this gap is so small that it prevents most fluid molecules from passing through the upstream valve 205 yet the gap is large enough to avoid wear. For instance, in an embodiment of the invention, a resistor and voltage source (not shown) can be utilized. The resistor can be placed between the upstream valve element 217 and the voltage source. When the upstream valve graphene drum 207 comes within tunneling current distance (such as around 0.3 to 1 nanometers) of upstream valve element 217, the tunneling current will flow through upstream valve graphene drum 207, upstream valve element 217 and the resistor. This tunneling current in combination with the resistor will lower the voltage between upstream valve element 217 and upstream valve graphene drum 207, thus lowering the electrostatic force between upstream valve element 217 and upstream valve graphene drum 207. If upstream valve graphene drum upstream valve graphene drum moves away from upstream valve graphene 217, the tunneling current will drop and the voltage/force between upstream valve graphene drum 207 and upstream valve element 217 will increase. Thus a 0.3 to 1 nanometer gap between upstream valve graphene drum 207 and upstream valve element 217 is maintained passively which allows the valve to close without causing mechanical wear between upstream valve graphene drum 207 and upstream valve element 217.
With respect to downstream valve 206, downstream valve element 218 can be utilized similarly.
In further embodiments, while not shown, standard silicon elements (such as transistors) can be integrated within or near the insulating material 103 near the respective graphene drums (main diaphragm graphene drum 201, upstream valve graphene drum 207, or downstream valve graphene drum 212) to help control the respective graphene drum and gate set.
FIG. 4 depicts another embodiment of a graphene-drum pump system illustrated in the PCT US11/23618 Application (described in paragraphs [00124]-[00127] and in FIG. 7-8, therein). FIG. 5 depicts the graphene-drum pump system of FIG. 4 with the graphene drum in a different position.
In FIGS. 4-5 (which are similar to FIGS. 7-8 of the PCT US11/23618 Application), an alternate embodiment of the present invention is shown that locates the graphene drum 201 such that the cavity 202 (in FIG. 2) is separated into two sealed cavities. (The change of position of graphene drum 201 is shown in FIGS. 4-5). Per the orientation of FIGS. 4-5, graphene drum 201 seals an upper cavity 401 and a lower cavity 402. As shown in FIGS. 4-5, upstream valve 205 and the downstream valve 206 are positioned to allow the pumping of fluid in and out of upper cavity 401.
As depicted in FIGS. 4-5, lower cavity 402 is oriented between the graphene drum 201 and the gate 203. Lower cavity 402 can be evacuated to increase the breakdown voltage between the graphene drum 201 and the gate 203. The maximum force (and thus the maximum graphene drum displacement) between the graphene drum 201 and the gate 203 increases as the square of this voltage. Thus, the pumping speed of the device 400 will increase significantly with an increase in the maximum allowable voltage.
As noted above, upper cavity 401 can be filled with air or some other gas/fluid that is being pumped. The vacuum in the lower cavity 402 can be created prior to mounting the graphene drum 201 over the main opening and maintained with a chemical getter. Small channels (not shown) between the lower cavities 402 could be routed to an external vacuum pump to create and maintain the vacuum. A set of dedicated graphene drum pumps mounted in the plurality of graphene drum pumps could also be used to create and maintain vacuum in the lower chambers (since pumping volume is so low these dedicated graphene drum pumps could operate with air in their lower chambers).
Similar to other embodiments shown in the PCT US11/23618 Application, in FIGS. 4-5, graphene drum 201 can act like a giant spring: i.e., once the gate 203 pulls graphene down (as shown in FIG. 4), when released the graphene drum 201 will spring upward (as shown in FIG. 5).
FIG. 6 depicts another embodiment of a graphene-drum pump system illustrated in the PCT US11/23618 Application (described in paragraphs [00129]-[00131] and in FIG. 9, therein). The graphene-drum pump system 600 shown in FIG. 6 can be actuated without requiring feedback as described above with respect to FIG. 2. In this embodiment, non-conductive member 604 (such as oxide) is placed between the graphene drum 201 and metallic gate 601 so that the graphene drum 201 cannot go into runaway mode and so that graphene drum 201 will not vigorously impact metallic gate 601 when seating. In embodiments of the invention, setting the graphene drum 201 (non-deflected) to metallic gate 901 distance to 20% of the diameter of the graphene drum 201 will prevent runaway (for a maximum deflection that is in the order of 10% of diameter of the graphene drum 201) and will allow the graphene drum 201 to seat softly on a surface of the non-conductive member 604 (such as oxide) without the need for feedback.
As shown in FIG. 6, when the graphene drum 201 is an open position, fluid can flow either (a) in inlet/outlet 602, through cavity 202, and out outlet/inlet 603 or (b) in outlet/inlet 603, through cavity 202, and out inlet/outlet 902 (due to the pressure differential between inlet/outlet 902 and outlet/inlet 903).
As shown in FIG. 6, the metallic gate 601 and metallic trace 605 have a non-conductive member 606 (such as oxide) between them. A voltage source 607 can be placed between the metallic gate 601 and the metallic trace 605 operatively connected to the graphene drum 201. The non-conductive member 604 physically prevents the graphene drum 201 and the metallic gate 601 from coming in contact with one another. This would prevent potentially damaging impacts of the graphene drum 201 and metallic gate 601.
While not illustrated here, in further embodiments of graphene-drum pump systems shown in the PCT US11/23618 Application, such systems can be designed to prevent the graphene drum and metallic gate from coming in contact. For instance, the graphene drum could be located at a distance such that its stiffness that precludes the graphene drum from being deflected to the degree necessary for it to come in contact with metallic gate. In such instance, the graphene drum would still need to be located such that it can be in the open position and the closed position. Or, a second and stabilizing system can be included in the embodiment of the invention that is operable for preventing the graphene drum from coming in contact with the gate.
Such embodiments of graphene-drum pump systems illustrated in the PCT US11/23618 Application can be used as a pump to displace fluid. As discussed in the PCT US11/23618 Application, this includes the use of such embodiments in a speaker, such as a compact audio speaker. While the graphene drums operate in the MHz range (i.e., at least about 1 MHz), the graphene drums can produce kHz audio signal by displacing air from one side and pushing it out the other (and then reversing the direction of the flow of fluid at the audio frequency). Utilizing such an approach: (a) provides the ability to make very low and very high pitch sounds with the same and very compact speaker; (b) provides the ability to make high volume sounds with a very small/light speaker chip; and (c) provides a little graphene speaker that would cool itself with high velocity airflow. Accordingly, these graphene-drum pump systems (of PCT US11/23618 Application) solve some of the problems of conventional speakers (such systems are efficient, compact, and can produce sound over the full range of audio frequencies without a loss of sound quality).
However, it has been found that such electrically conductive membrane transducers (of PCT US11/23618 Application) have limitations because these systems requires air to flow from the back of the chip/wafer to the front of the chip/wafer. Furthermore, these systems also require the valves to operate properly. Accordingly, there is a need to simplify the design of electrically conductive membrane transducers to reduce their complexity and cost. Furthermore, there is a need to reduce and/or eliminate the contacting and wear of the elements that occurs in these systems of PCT US11/23618 Application.
The two main advantages of the current graphene membrane transducer are that it can draw/push air in/out the same vents (allowing everything to be on one side of the chip/wafer if desired) and the system does not require valves to work. These two simplifications result in much lower complexity and cost. Also, there are no contacting/wear elements in the current invention. Since the graphene membrane transducer sends audio waves out from one face of a chip, there is no need to mount the device in a bulky enclosure (the backside of conventional cone speakers must be sealed to stop oppositely phased sound from canceling front-facing sound). If graphene membrane transducers assemblies are mounted on both sides of a chip, it is also possible to cancel reaction forces (by producing sound waves in phase from each side) and thus unwanted vibration.
SUMMARY OF THE INVENTION
The present invention relates to an electrically conductive membrane transducer. The electrically conductive membrane can be, for example, graphene membrane.
In general, in another aspect, the invention features an audio speaker that includes an array of membrane pumps. The membranes of the membrane pumps are electrically conductive membranes. The audio speaker further includes one or more electrically conductive traces located near the electrically conductive membranes. The audio speaker further includes a first time varying voltage between the electrically conductive membranes and at least some of the one or more electrically conductive traces. The time varying voltage is operable for moving the electrically conductive membranes in the array toward and away from electrically conductive membrane first positions. The combined movement of the electrically conductive membranes toward and away from the electrically conductive membrane first positions is operable to cause a fluid to enter and exit a chamber of the audio speaker that increases and decreases pressure in the chamber. The audio speaker further includes a large membrane that bounds a portion of the chamber. The increase and decrease of the pressure in the chamber is operable to move the large membrane toward and away from the large membrane first position. The movement of the large membrane is operable to produce an audio signal at a desired frequency.
Implementations of the invention can include one or more of the following features:
The combined movement of the electrically conductive membranes in the array toward the electrically conductive membrane first positions can be operable to cause the fluid to enter the chamber of the audio speaker that increases the pressure in the chamber. The increase of the pressure in the chamber can be operable to move the large membrane toward the large membrane first position. The combined movement of the electrically conductive membranes in the array away from the electrically conductive membrane first position can be operable to cause the fluid to exit the chamber of the audio speaker that decreases the pressure in the chamber. The decrease of the pressure in the chamber can be operable to move the large membrane away from the large membrane first position.
The combined movement of the electrically conductive membranes in the array toward the electrically conductive membrane first positions can be operable to cause the fluid to exit the chamber of the audio speaker that decreases the pressure in the chamber. The decrease of the pressure in the chamber can be operable to move the large membrane toward the large membrane first position. The combined movement of the electrically conductive membranes in the array away from the electrically conductive membrane first position can be operable to cause the fluid to enter the chamber of the audio speaker that increases the pressure in the chamber. The increase of the pressure in the chamber can be operable to move the large membrane away from the large membrane first position.
The time varying voltage can be operable for moving the electrically conductive membranes in the array toward the electrically conductive membrane first positions while moving the electrically conductive membranes in the array away from electrically conductive membrane second positions. The time varying voltage can be operable for moving the electrically conductive membranes in the array toward the electrically conductive membrane second positions while moving the electrically conductive membranes in the array away from the electrically conductive membrane first positions. The combined movement of the electrically conductive membranes toward the electrically conductive membrane first positions can be operable to cause the fluid to enter the chamber of the audio speaker to increase pressure in the chamber. The combined movement of the electrically conductive membranes toward the electrically conductive membrane second positions can be operable to cause the fluid to exit the chamber of the audio speaker to decrease pressure in the chamber. The increase of the pressure in the chamber can be operable to move the large membrane toward the large membrane first position. The decrease of the pressure in the chamber can be operable to move the large membrane toward the large membrane second position.
The electrically conductive membranes can each be less than 10 microns thick.
The electrically conductive membranes can include a graphene-polymer composite.
The electrically conductive membranes can include a metal-polymer composite.
The electrically conductive membranes can include a material selected from the group consisting of graphene, graphene/graphene oxide composites, graphene-polymer composites, and metal-polymer composites.
The one or more electrically conductive traces can each include metal.
The large membrane can include a polymer.
The polymer can include PDMS.
The polymer can include latex.
The electrically conductive membranes can take between around 50 milliseconds and around 50 microseconds to move toward and away the electrically conductive membrane first position.
The electrically conductive membranes can take between around 50 milliseconds and around 50 microseconds to move back and forth between the electrically conductive membrane first positions and the electrically conductive membrane second positions.
The audio signal can be between 20 Hz and 20 kHz.
The large membrane can have a diameter between around 0.5 cm to 5 cm.
The electrically conductive membranes each can have a diameter between around 0.5 mm to 5 mm.
The ratio of diameters of the large membrane and the electrically conductive membranes can be between 2:1 and 100:1.
The ratio of diameters of the large membrane and the electrically conductive membranes can be between 5:1 and 20:1
The fluid can be air.
DESCRIPTION OF DRAWINGS
FIG. 1 depicts a perspective view of a graphene-drum pump system illustrated in PCT US11/23618 Application.
FIG. 2 depicts a close-up of a graphene-drum pump (in the graphene-drum pump system of FIG. 1) in exhaust mode.
FIG. 3 depicts a close-up of a graphene-drum pump (in the graphene-drum pump system of FIG. 1) in intake mode.
FIG. 4 depicts an alternative embodiment of a graphene-drum pump system.
FIG. 5 depicts the graphene-drum pump system of FIG. 4 with the graphene drum in a different position.
FIG. 6 depicts a further alternative embodiment of a graphene-drum pump system.
FIG. 7 illustrates an array of graphene membrane transducers of the present invention, which includes a magnified illustrated view of one of the graphene membrane transducers.
FIG. 8A depicts a cross-sectional (a-a′) illustration of the magnified graphene membrane transducer illustrated in FIG. 7.
FIG. 8B depicts a cross-sectional (b-b′) illustration of the magnified graphene membrane transducer illustrated in FIG. 7.
FIG. 8C depicts a cross-sectional (c-c′) illustration of the magnified graphene membrane transducer illustrated in FIG. 7.
FIGS. 9A-9C depict an illustration of a graphene membrane transducer (illustrated in FIG. 7) that shows how the graphene membrane moves to cause fluid flow. FIG. 9A illustrates the graphene membrane transducer before an electrostatic forces are applied. FIG. 9B illustrates the graphene membrane transducer when the graphene membrane is being pulled toward the conductive trace due to electrostatic forces. FIG. 9C illustrates the graphene membrane transducer after the electrostatic forces applied in FIG. 9B are reduced or eliminated.
FIG. 10 depicts a normalized graph that shows how the gate voltage, graphene membrane height, and audio power change over a two cycle period in an embodiment of the present invention.
FIG. 11 illustrates an alternative array of graphene membrane transducers of the present invention, which includes a magnified illustrated view of one of the graphene membrane transducers.
FIG. 12 depicts a cross-sectional (a-a′) illustration of the magnified graphene membrane transducer illustrated in FIG. 11.
FIGS. 13A-13B depict an illustration of a graphene membrane transducer (illustrated in FIG. 11) that shows how the graphene membrane moves to cause fluid flow. FIG. 13A illustrates the graphene membrane transducer when the graphene membrane is being pulled toward the conductive trace due to electrostatic forces. FIG. 13B illustrates the graphene membrane transducer after the electrostatic forces applied in FIG. 13A are reduced or eliminated.
FIG. 14 illustrates another alternative array of graphene membrane transducers of the present invention, which includes a magnified illustrated view of one of the graphene membrane transducers.
FIG. 15 depicts a cross-sectional (a-a′) illustration of the magnified graphene membrane transducer illustrated in FIG. 14.
FIGS. 16A-16B depicts an illustration of a graphene membrane transducer (illustrated in FIG. 14) that shows how the graphene membrane moves to cause fluid flow. FIG. 16A illustrates the graphene membrane transducer when the graphene membrane is being pulled toward the conductive bottom trace due to electrostatic forces. FIG. 16B illustrates the graphene membrane transducer after the electrostatic forces applied in FIG. 16A are reduced or eliminated and when the graphene membrane is being pulled toward the top trace due to electrostatic forces.
FIG. 17 illustrates another alternative array of graphene membrane transducers of the present invention, which includes a magnified illustrated view of two of the graphene membrane transducers.
FIG. 18A depicts a cross-sectional (a-a′) illustration of the magnified graphene membrane transducer illustrated in FIG. 17.
FIG. 18B depicts a cross-sectional (b-b′) illustration of the magnified graphene membrane transducer illustrated in FIG. 17.
FIG. 19 depicts an illustration of a graphene membrane transducer (illustrated in FIG. 17) that shows how the graphene membrane moves to cause fluid flow.
FIG. 20 illustrates another alternative array of graphene membrane transducers of the present invention, which includes a magnified illustrated view of one of the graphene membrane transducers.
FIG. 21 depicts a cross-sectional (a-a′) illustration of the magnified graphene membrane transducer illustrated in FIG. 20.
FIGS. 22A-22B depict an illustration of a graphene membrane transducer (illustrated in FIG. 19) that shows how the graphene membrane moves to cause fluid flow. FIG. 22A illustrates the graphene membrane transducer when the graphene membrane is being pulled toward the conductive trace due to electrostatic forces. FIG. 22B illustrates the graphene membrane transducer after the electrostatic forces applied in FIG. 22A are reduced or eliminated.
FIGS. 23A-23I depict an illustration of a method by which an embodiment of the graphene membrane transducer can be built.
FIG. 24 depicts a system showing a venturi effect.
FIGS. 25A-25B depict illustrations of a graphene membrane pump/transducer that utilizes a venturi channel and that shows how the graphene membranes move to cause fluid flow.
FIG. 26 depicts an electrically conductive membrane pump/transducer that utilizes an array of electrically conductive membrane pumps that cause a larger membrane to move in phase.
DETAILED DESCRIPTION
The present invention relates to an improved electrically conductive membrane transducer, such as, for example, an improved graphene membrane transducer. The improved electrically conductive membrane transducer does not require air (or other fluid) to flow from the back of the chip/wafer to the front of the chip/wafer. Furthermore, the improved electrically conductive membrane does not require valves to operate. Other advantages of the present invention is that the electrically conductive membrane transducer can draw/push air in/out the same vents (allowing everything to be on one side of the chip/wafer if desired). These simplifications result in much lower complexity and cost.
Also, there is no contacting/wear elements in the current invention.
Moreover, the electrically conductive membrane transducer sends audio waves out from one face of a chip; thus there is no longer any requirement to mount the device in a bulky enclosure (the backside of conventional cone speakers must be sealed to stop oppositely phased sound from canceling front-facing sound).
Furthermore, it is also possible to cancel reaction forces (by producing sound waves in phase from each side) and thus unwanted vibration, by mounting the electrically conductive membrane transducer assemblies on both sides of a chip.
In the preceding and following discussion of the present invention, the electrically conductive membrane of the electrically conductive membrane transducer will be a graphene membrane. However, a person of skill in the art of the present invention will understand that other electrically conductive membranes can be used in place of, or in addition to, graphene membranes (such as in graphene oxide membrane and graphene/graphene oxide membranes).
Referring to the figures, FIG. 7 illustrates an array 700 of graphene membrane transducers 701, which includes a magnified illustrated view 702 of one of the graphene membrane transducers 701. Magnified illustrated view 702 provides dotted lines 703, 704, and 705, which define a cross section a-a′, b-b′, c-c′, respectively.
FIG. 8A depicts the cross-sectional (a-a′) illustration of the magnified graphene membrane transducer 701 illustrated in FIG. 7. As shown in FIG. 8A, a graphene membrane 801 rests upon and is electrically connected to metallic gate 802. As shown in the orientation of FIG. 8A, the center portion of graphene membrane 801 is above a metallic trace 803 with a cavity 804 between the center of graphene membrane 801 and metallic trace 803. As shown in FIG. 6, the metallic gate 802 and metallic trace 803 have a non-conductive member 805 (such as oxide) between them.
FIG. 8B depicts a cross-sectional (b-b′) illustration of the magnified graphene membrane transducer illustrated in FIG. 7.
FIG. 8C depicts a cross-sectional (c-c′) illustration of the magnified graphene membrane transducer illustrated in FIG. 7. Per the orientation of FIG. 8C, cavity 804 is in fluid communication with cavity 807 by vented wall 809, and cavity 807 is also bounded by top 806 with vent holes 808. (Per the orientation of FIG. 8C, the vent holes 808 are at the top of cavity 807).
FIGS. 9A-9C depict an illustration of a graphene membrane transducer 701 (illustrated in FIG. 7) that shows how the graphene membrane moves to cause fluid flow. FIG. 9A is the same view as FIG. 8C and illustrates the graphene membrane transducer 701 before an electrostatic forces are applied. As shown in FIG. 9A, the center of graphene membrane 801 is not deflected.
FIG. 9B illustrates the graphene membrane transducer 701 when the graphene membrane 801 is being pulled toward metal trace 803 due to electrostatic forces. In the orientation shown in FIG. 9B, the graphene membrane 801 is being deflected down toward metal trace 803 (as shown by arrows 901). A voltage between the electrically conductive trace 803 and graphene membrane 801 is used to rapidly deflect the graphene membrane 801 downward. This deflection reduces the volume of cavity 804, thereby causing a fluid to flow from cavity 804 to cavity 807 via vented wall 809, as shown by arrow 902. This fluid flow thereby pushes fluid outside cavity 807, via vents 808 of top 806, as shown by arrow 903, which produces waves 904.
In an alternative embodiment, cavity 804 and cavity 807 are not separated by wall 809 (i.e., cavity 804 and cavity 807 are the same cavity).
In a further embodiment, wall 809 is not vented, but rather a membrane that can deflect (i.e., cavity 804 and cavity 807 are isolated from one another). In such instance, when graphene membrane 801 is deflected downward, the increase in pressure inside chamber 804 caused wall 809 to deflect into cavity 807, thereby raising the pressure inside cavity 807. This increased pressure thereby causes fluid to be pushed outside cavity 807, via vents 808 of top 806, as shown by arrow 903, which produces waves 904.
FIG. 9C illustrates the graphene membrane transducer 701 after the electrostatic forces applied in FIG. 9B are reduced or eliminated. When the voltage between the electrically conductive trace 803 and graphene membrane 801 is reduced or eliminated, the graphene membrane 801 will move back to its original position (as shown by arrows 905). When doing so, the decrease in pressure inside cavity 804 (and thereby cavity 807) will allow for the fluid to flow back into cavity 807 and cavity 804, as shown by arrows 906 and 907, respectively. Generally, the rate of this flow back is relatively slow, as compared to the rate at which the fluid flowed out as shown in FIG. 9B.
FIG. 10 depicts a graph that shows how the gate voltage, graphene membrane height, and audio power change over a two cycle period in an embodiment of the present invention. Gate voltage, graphene membrane height, and audio power are shown in normalized curves 1001, 1002, and 1003, respectively. (These curves have been normalized so that they can be shown on the same graph). The graphene height is the height of the graphene membrane 801 measured relative to the metallic trace 803 (as shown in FIGS. 9A-9C).
The first cycle includes (a) a period 1004 in which in which the gate voltage is rapidly increased, (b) a period 1005 in which the gate voltage is more slowly reduced back to zero, and (c) a period 1006 in which the gate voltage is maintained at zero. The second cycle repeats these periods 1004, 1005, and 1006.
When rapidly increasing the gate voltage during period 1004, the graphene membrane 801 is pulled down rapidly (toward metallic trace 803). When more slowly reducing the gate voltage in period 1005, graphene membrane 801 is let up more slowly. Thus, by shaping the gate voltage appropriately, the rate of movement upward and downward of the graphene membrane is controlled.
Curve 1003 shows how the expelled air power (a combination of the net velocity of the air molecules and the elevated temperature of the expelled air molecules) or audio power is high during the first part of the cycle (peaking at the end of period 1004) and then actually goes negative around a third of the way through the cycle. The reason the air/audio power is negative during the air intake part of the cycle is because the intake air is being cooled as cavity 804 expands. As you can be seen from the relative height of the pulses, the net audio power is positive.
If each of these cycles takes one microsecond, it would take 500 of these cycles to build up the high pressure part of a 1 kHz audio wave. The graphene membrane transducer array (such as array 700) may be driven harder during certain parts of the 500 cycles (and some graphene membrane transducers may be out of phase with other graphene membrane transducers) to better approximate a smooth audio wave.
FIG. 11 illustrates an array 1100 of alternative graphene membrane transducers 1101, which includes a magnified illustrated view 1102 of one of the graphene membrane transducers 1101. Magnified illustrated view 1102 provides dotted line 1103, which defines a cross section a-a′.
FIG. 12 depicts the cross-sectional (a-a′) illustration of the magnified graphene membrane transducer 1101 illustrated in FIG. 11. Similar to graphene membrane transducer 701, graphene membrane transducer 1101 has graphene membrane 801, metallic gate 802, metallic trace 803, cavity 804, and non-conductive member 805. As shown in FIG. 12, graphene membrane transducer 1101 also has a vent hole 1201 through which fluid may flow out of cavity 804. By this arrangement of vent hole 1201, the density of graphene membrane transducers 1101 can be increased in array 1100 (as compared to the density of graphene membrane transducers 701 in array 700).
FIG. 13A illustrates the graphene membrane transducer 1101 when the graphene membrane 801 is being pulled toward metal trace 803 due to electrostatic forces. In the orientation shown in FIG. 13A, the graphene membrane 801 is being deflected down toward metal trace 803 (as shown by arrows 1301). As with graphene membrane transducer 701, a voltage between the electrically conductive trace 803 and graphene membrane 801 is used to rapidly deflection the graphene membrane 801 downward. This deflection reduces the volume of cavity 804, thereby causing a fluid to flow out of cavity 804 through vent hole 1201, as shown by arrow 1302, which produces waves 1303.
FIG. 13B illustrates the graphene membrane transducer 1001 after the electrostatic forces applied in FIG. 13A are reduced or eliminated. When the voltage between the electrically conductive trace 803 and graphene membrane 801 is reduced or eliminated, the graphene membrane 801 will move back to its original position (as shown by arrows 1305). When doing so, the decrease in pressure inside cavity 804 will allow for the fluid to flow back into cavity 804, as shown by arrow 1304. Similar to graphene membrane transducer 701, generally, the rate of this flow back is relatively slow, as compared to the rate at which the fluid flowed out as shown in FIG. 13A.
FIG. 14 illustrates an array 1400 of alternative graphene membrane transducers 1401, which includes a magnified illustrated view 1402 of one of the graphene membrane transducers 1401. Magnified illustrated view 1402 provides dotted line 1403, which defines a cross section a-a′.
FIG. 15 depicts the cross-sectional (a-a′) illustration of the magnified graphene membrane transducer 1401 illustrated in FIG. 14. Similar to graphene membrane transducer 701 and graphene membrane transducer 1101, graphene membrane transducer 1401 has graphene membrane 801, metallic gate 802, metallic trace 803, cavity 804, and non-conductive member 805. As shown in FIG. 15, graphene membrane transducer 1401 also has a cavity 1501 and a vent hole 1502 through which fluid may flow out of cavity 1501. Furthermore, graphene membrane transducer 1401 also a second metallic trace 1503 with a non-conductive member 1504 (such as oxide) between them.
FIG. 16A illustrates the graphene membrane transducer 1401 when the graphene membrane 801 is being pulled toward metal trace 803 due to electrostatic forces. In the orientation shown in FIG. 16A, the graphene membrane 801 is being deflected down toward metal trace 803 (as shown by arrows 1601). As with graphene membrane transducer 701, a voltage between the electrically conductive trace 803 and graphene membrane 801 is used to deflect the graphene membrane 801 downward. If V2 is set to ground, this deflection is caused by increasing the voltage at V3. This deflection reduces the volume of cavity 804 (increasing the pressure inside cavity 804) and increases the volume of cavity 1501, thereby causing a fluid to flow into cavity 1501 through vent hole 1502, as shown by arrow 1502.
FIG. 16B illustrates the graphene membrane transducer 1401 after the electrostatic forces applied in FIG. 16A are reduced or eliminated and when the graphene membrane 801 deflected back toward the second metallic trace 1503 due to electrostatic forces. When the voltage between the electrically conductive trace 803 and graphene membrane 801 is reduced or eliminated (such as by reducing the voltage at V3) and the voltage between second metallic trace 1503 and graphene membrane 801 is increased (such as by increasing the voltage at V1) the graphene membrane 801 will deflect back toward the second metallic trace 1503 (as shown by arrows 1603). When doing so, the increase in pressure inside cavity 1501 will cause to flow out of cavity 1501 through vent hole 1502, as shown by arrow 1604, which produces waves 1605.
Typically, a gas is maintained in cavity 804, which is sealed. Since the gas in cavity 804 is compressed beneath the graphene membrane 801 as fluid is drawn in the vent hole 1502 (as shown in FIG. 16A), per the orientation of FIGS. 16A-16B, this produces an upward pressure on the graphene membrane 801 that can help push the fluid out of the vent hole 1502 during the exhaust phase shown in FIG. 16B. The mechanical restoration force of the graphene membrane 801 also aids in pushing fluid out the vent hole 1502 along with the electrostatic force between the graphene membrane 801 and the second metallic trace 1503.
Graphene membrane transducer 1401 is also capable of cooling the fluid (such as air) if the graphene membrane 801 is pulled down rapidly (as shown in FIG. 16A) and raised slowly back up toward the vent hole (as shown in FIG. 16B). In this embodiment the graphene membrane transducer could thus be used to create the low density or cool portion of a sound wave or just be used for cooling in general.
Calculations show the ratio of graphene membrane area to vent area should be about ten to about 100 and the mechanical frequency of the graphene membrane should be on the order of 1 MHz for a 25μ diameter graphene drum.
The main operating principle is that air (or other fluid) is drawn in slowly and pushed out quickly (push out time is about three times to about ten times faster than the draw in time). To make a 1 kHz audio signal, an array (thousands to millions) of graphene membrane transducers should cycle about 500 times for each positive portion of the audio wave at on the order of 1 MHz. A cycle includes drawing in air or other fluid and pushing the air or other fluid out over a period of time. For example, a cycle could include drawing in air or other fluid for about 850 ns and pushing the air or other fluid out for about 150 ns over a half a millisecond period to produce the high pressure part of audio wave and then not pumping for another half a millisecond to “produce” the low pressure part of sound wave.
Although the 1 MHz component of the wave is contained within lower frequency audio wave, it cannot be perceived by the human ear. Thus, in some embodiments, the transducer can be an ultrasonic transducer. However, when needed, groups of graphene membrane transducers can be pumped out of phase from each other to cancel the MHz component of the audio wave, thus yielding waves audible to the human ear.
Furthermore, if desired, embodiments of the present invention can be optically transparent and flexible. For example, the primary substrate could be glass in place of silicon and the metal traces could be made of graphene. Mounting speakers on top of display screens may be attractive in some applications (like cell phone, computer and TV screens). The reaction force of the graphene membrane transducers can also be used to levitate and position the graphene membrane transducer array (i.e., the speakers could be directed to position themselves in three dimensions within a room or outdoor arena).
FIG. 17 illustrates another alternative array 1700 of graphene membrane transducers of the present invention, which includes a magnified illustrated view of two of the graphene membrane transducers 1701. Magnified illustrated view 1702 provides dotted lines 1703 and 1704, which define a cross section a-a′ and b-b′, respectively.
FIGS. 18A-18B depict cross-sectional illustrations (a-a′ and b-b′, respectively) of the magnified graphene membrane transducer 1701 illustrated in FIG. 17. Similar to graphene membrane transducer 701, graphene membrane transducer 1101, and graphene membrane transducer 1401, graphene membrane transducer 1701 has graphene membrane 801, metallic trace 803, cavity 804, and non-conductive member 805. In this embodiment, graphene membrane 801 spans two conductive traces (trace 1801 and trace 1802, which can be metallic traces). The space between trace 1801 and trace 1802 forms two vents. One of these vents (vent 1803) is shown in FIG. 18B. The other vent is not shown in FIG. 18B, as it is on the opposing side of graphene membrane transducer 1701.
By placing a voltage 1804 across trace 1801 and trace 1802, current 1805 (generally in the kHz range and in a range closely related to the desired audio signal) can be applied from one trace (trace 1801), through the graphene membrane 801, and into the other trace (trace 1802), which will heat the graphene membrane 801 (via resistance heating). In graphene membrane transducer 1701, the majority of current 1805 will run across the vent 1803 and the other vent because this is the path of least resistance (and where most of the resistive heating will take place).
FIG. 19 illustrates the graphene membrane transducer 1701 when the graphene membrane 801 is being pulled toward metal trace 803 (as shown by arrows 1901) due to electrostatic forces (i.e, by placing a voltage 1902 between graphene 801 and metallic trace 803). Such voltage 1901 can have a frequency in the MHz range, which will make the graphene membrane transducer 1701 pump air in and out of vent 1803 and the other in the order of 100 m/s (which will remove the heat from the graphene membrane 801 and impart it to the surrounding air).
Accordingly, metallic trace 803 can be used to make the graphene membrane 801 oscillate (such as in the MHz range), which will force cooling air across the graphene membrane 801 (and will heats this airflow). Such a system can be used to enhance the transducer mode of the present invention or can be used in a thermo-acoustic mode of the present invention.
FIG. 20 illustrates an array 2000 of another alternative graphene membrane transducers 2001, which includes a magnified illustrated view 2002 of one of the graphene membrane transducers 2001. Magnified illustrated view 2002 provides dotted line 2003, which defines a cross section a-a′.
FIG. 21 depicts the cross-sectional (a-a′) illustration of the magnified graphene membrane transducer 2001 illustrated in FIG. 17. Similar to graphene membrane transducer 701, graphene membrane transducer 1101, and graphene membrane transducer 1401, graphene membrane transducer 2001 has graphene membrane 801, metallic gate 802, metallic trace 803, cavity 804, and non-conductive member 805. As shown in FIG. 21, graphene membrane transducer 2001 is similar to graphene membrane 1101 except that it does not have a vent hole 1201.
FIG. 22A illustrates the graphene membrane transducer 2001 when the graphene membrane 801 is being pulled toward metal trace 803 due to electrostatic forces. In the orientation shown in FIG. 22A, the graphene membrane 801 is being deflected down toward metal trace 803 (as shown by arrows 2201). As with graphene membrane transducer 1101, a voltage between the electrically conductive trace 803 and graphene membrane 801 is used to deflect the graphene membrane 801 downward. This deflection reduces the volume of cavity 804, thereby increasing the pressure inside cavity 804, which is sealed and filled with a gas.
FIG. 22B illustrates the graphene membrane transducer 2001 after the electrostatic forces applied in FIG. 22A are reduced or eliminated. When the voltage between the electrically conductive trace 803 and graphene membrane 801 is reduced or eliminated, the graphene membrane 801 will move back to its original position (as shown by arrows 2202).
As discussed above, a gas is maintained in cavity 804, which is sealed. Since the gas in cavity 804 is compressed beneath the graphene membrane 801 as (as shown in FIG. 22A), per the orientation of FIGS. 22A-22B, this produces an upward pressure on the graphene membrane 801 that can will push the fluid up as during the phase shown in FIG. 22B (as shown by waves 2201).
This system can replace piezoelectric transducers used in conventional liquid ultrasonic applications such as medical imaging. Graphene membrane 801 can be made of several layers of graphene to insure that a water-tight seal is maintained between the graphene and cavity 804.
This system can produces ultrasonic waves at a frequency equal to the mechanical frequency of the graphene membranes.
A significant advantage over prior art ultrasonic transducers is that the present invention has the ability to operate over a wide range of frequencies without losing efficiency. Moreover, the system of the present invention does not need to operate in mechanical resonance, which is often the case with piezoelectric ultrasonic transducers.
Moreover, if some electrically conductive particles are deposited on the electrically conductive trace 803, field emission current between the moveable graphene and these trace particles can be used to sense ultrasonic vibrations in a fluid or gas (i.e., graphene membrane 801 will oscillate in response to pressure changes and these mechanical oscillations will cause a field emission or tunneling currents to oscillate at this same frequency).
FIGS. 23A-23I depict an illustration of a method by which an embodiment of the graphene membrane transducer can be built. It should be noted that FIGS. 23A-23I show how graphene can be used as scaffolding to build up layered devices (containing voids) without using problematic/expensive chemical mechanical polishing. Although the process shown in the figures is used to build a graphene membrane transducer (in this case graphene membrane transducer 1301 as shown in FIG. 14), this process is generally applicable to any MEMS/NEMS device that requires one or more layers with voids.
As illustrated in FIGS. 23A-23I, material 2301 can be silicon or glass, material 2302 is a metal (like tungsten), material 2303 is an electrical insulator (like oxide), the material 2304 is a metal (like gold), and the material 2305 is graphene.
FIG. 23A illustrates a layered substrate from top to bottom of gold 2304, tungsten 2302, oxide 2303, tungsten 2302, and silicon 2301.
FIG. 23B illustrates a layered substrate in which portions of the top layers of gold 2304, tungsten 2302, oxide 2303 were removed by techniques known in the art. The exposed layer of tungsten that has not been removed is metal trace 803 of graphene membrane transducer 1301. Moreover, the portion of oxide 2303 that remains is non-conductive member 805 of graphene membrane transducer 1301.
FIG. 23C illustrates the positioning of a graphene membrane 2305 on top of the layered substrate shown in FIG. 23B. Techniques to transfer and position graphene membranes over target features are disclosed and taught in pending and co-owned U.S. patent application Ser. Nos. 13/098,101 (Lackowski et al.) and 61/427,011 (Everett et al.). This graphene membrane is the graphene membrane 801 of graphene membrane transducer 1301. Moreover, the cavity formed below graphene membrane 2305 in FIG. 23C is cavity 804 of graphene membrane transducer 1301.
FIG. 23D illustrates depositing tungsten 2302 on top of graphene membrane 2305 using techniques known in the art. The combination of the tungsten 2305 and gold 2304 about the graphene membrane is the metallic gate 802 of graphene membrane transducer 1301.
FIG. 23E illustrates depositing oxide 2303 and then depositing tungsten 2302 on top of the oxide 2303 using techniques known in the art.
FIG. 23F illustrates the layered substrate in which portions of the top layers of tungsten 2302 and oxide 2303 were removed by techniques known in the art. The portion of oxide 2303 that remains is non-conductive member 1404 of graphene membrane transducer 1301.
FIG. 23G illustrates the positioning of a graphene membrane 2305 on top of the layered substrate shown in FIG. 23F using techniques known in the art. The cavity formed below graphene membrane 2305 in FIG. 23G is cavity 1401 of graphene membrane transducer 1301.
FIG. 23H illustrates depositing tungsten 2302 and then depositing oxide 2303 on top of the graphene membrane 2305 using techniques known in the art.
FIG. 23I illustrates the layered substrate in which portions of the top layers of oxide 2303, tungsten 2302, and graphene membrane 2305 were removed by techniques known in the art to form a hole. This hole is vent hole 1402 of graphene membrane transducer 1301. The portion of tungsten 2302 and graphene membrane 2305 that remains is the second metallic trace 1403 of graphene membrane transducer 1301.
Because graphene is just a few angstroms thick and adheres closely to almost any material, it does not cause significant ripples in the materials deposited on top of it (and thus does not require CMP between layers). Even though it is thin, graphene is strong enough to hold up the weight of materials many times its own weight. Once a thin layer of material like metal is deposited (and solidifies) on top of graphene, this new material can help support subsequent layers of material.
FIG. 24 depicts a system 2400 showing a venturi effect. This system 2400 has an inlet orifice 2403 (having a cross-sectional area (A1) 2401), an outlet orifice 2405 (having a cross-sectional area (A2) 2402), and a venturi channel 2404. The venturi channel 2404 is a constriction (i.e., the cross-sectional area of the venturi channel 2404 is less than cross-sectional area (A1) 2401 and cross-sectional area (A2) 2402, such that the velocity 2406 of the fluid flow through venturi channel 2404 is much higher, as compared with the velocity 2406 in the inlet orifice 2403 and outlet orifice 2405). The venturi channel 2404 also includes a venturi orifice 2410 that is exposed to a partial vacuum in the venturi channel 2404. The partial vacuum is illustrated in FIG. 24 by the change in height 2407 of the fluid 2408 in the venturi orifice 2410 and the connection 2409 to the outlet orifice 2405.
FIGS. 25A-25B depict illustrations of a graphene membrane pump/transducer 2500 that utilizes a venturi channel 2504 and that show how graphene membranes 2509 move to cause fluid flow. FIG. 25A illustrates the graphene membrane pump/transducer 2500 in the inflow process. Graphene membrane pump/transducer 2500 has an array of graphene membranes 2509 deflecting away from the substrate (i.e., to the left in the orientation of FIG. 25A) and thus pulling a fluid (such as air) into pump orifice 2503 (having cross-sectional area (A1) 2501) via the venturi channel 2504. This high velocity of fluid in the venturi channel 2504 (which can be, in some embodiments approximately 10-100 meters/second for airflow) creates a partial vacuum within the venturi channel 2504 and as a result some fluid (such as air) is drawn into the venturi channel 2504 via the venturi orifice 2510. The fluid flow in the pump orifice 2503, the outlet orifice 2505, and the venturi orifice 2510 are represented, respectively, by arrows 2506, 2507, and 2508. The inflow of fluid (such as air) that passes through the pump orifice 2503 (having cross-sectional area (A1) 2501) is the sum of the air flowing in from the outlet orifice 2505 and the air drawn into the venturi orifice 2510. Thus, the fluid flowing across cross-sectional area (A1) 2503 is greater than the fluid flowing across cross-sectional area (A2) 2505.
FIG. 25B illustrates the graphene membrane pump/transducer 2500 in the outflow process. When the graphene membranes 2509 move toward the substrate (i.e., to the right in the orientation of FIG. 25B) the direction of the fluid flow in the pump orifice 2503, the outlet orifice 2505, and the venturi channel 2504 reverses but the high velocity fluid moving through the venturi channel 2504 still creates a partial vacuum, which draws fluid into the venturi orifice 2510. The fluid flow in the pump orifice 2503 and the venturi orifice 2510 are represented, respectively, by arrows 2506 and 2508. The fluid flow in the outlet orifice 2505 is represented by arrows 2507A and 2507B. In the embodiment shown in FIG. 25B, the volume of fluid flowing through the pump orifice 2503 is less than the volume of gas flowing through the outlet orifice 2505.
Even though the air flowing through the pump orifice 2503 is on average zero (since the average inflow is equal to the average outflow), there is a net airflow that is exhausted through the outlet orifice 2505 due to the addition of the air flowing into the venturi orifice 2510.
This net airflow through the outlet orifice 2505 can be used to produce an audible sound wave (20 Hz to 20 kHz) even though the graphene membranes may have a mechanical frequency in the ultrasonic range (above 20 kHz). The average airflow exhausted through the outlet orifice 2505 can also be used to cool electronic components, produce thrust, or pump a fluid. Although an array of graphene membranes is shown in FIGS. 25A-25B, the graphene membrane pump/transducer 2500 would also operate with a single graphene membrane.
FIG. 26 depicts an electrically conductive membrane pump/transducer 2600 that utilizes an array of electrically conductive membrane pumps that cause a larger membrane 2602 to move in phase. Four of the electrically conductive membrane pumps of the electrically conductive membrane pump/transducer 2600 are illustrated in FIG. 26. Each of the electrically conductive membrane pumps has a membrane 2601 (such as a graphene-polymer membrane or metal-polymer composite membrane) that can deflect toward trace 2605 (as shown in the dashed curve 2601a) and that can deflect toward trace 2606 (as shown in the dashed curve 2601b). The traces 2604 and 2605 are a metal (like copper, tungsten, or gold). The electrically conductive membrane pumps also have a material 2603 (which can be plastic or Kapton) and material 2604 that is an electrical insulator (like oxide or Kapton).
Each of the electrically conductive membrane pumps in the array has chambers 2610 and 2611 that change in size as the electrically conductive membrane 2601 deflects between dashed curves 2601a and 2601b. As shown in FIG. 26, as electrically conductive membranes 2601 deflects toward trace 2605 (as shown in the dashed curve 2601a), (a) chamber 2610 reduces in size to expel air (or other fluid) through vent 2607 (and into chamber 2609) and (b) chamber 2611 increases in size to draw in air (or other fluid) through vent 2608. As electrically conductive membranes 2601 deflect toward trace 2606 (as shown in the dashed curve 2601b), (a) chamber 2610 increases in size to draw in air (or other fluid) through vent 2607 (and out of chamber 2609) and (b) chamber 2611 reduces in size to expel air (or other fluid) through vent 2608.
Chamber 2609 is bounded in part by the array of electrically conductive membrane pumps and a membrane 2602 (which is larger than the electrically conductive membranes 2601). Membrane 2602 can be made of a polymer material, like PDMS (polydimethylsiloxane) or latex. Membrane 2602 is generally on the order of 0.5 to 5 centimeters in diameter, and is much larger as compared to the electrically conductive membranes 2601, which are generally on the order of 0.5 to 5 millimeters in diameter. Typically, the ratio of the diameters between the membrane 2602 and the electrically conductive membrane 2601 is between 2:1 and 100:1, and more typically between 5:1 and 20:1. Vents 2607 allow air (or other fluid) be expelled into and withdrawn from chamber 2609 in response to the deflection of the electrically conductive membranes 2601 of the electrically conductive membrane pumps of the array.
The array of electrically conductive membrane pumps creates pressure changes in the chamber 2609 (increasing pressure as gas (or other fluid) is expelled into the chamber 2609 and reducing pressure as gas (or other fluid) is drawn out of the chamber 2609). These pressure changes cause membrane 2602 to move approximately in phase with the motion of the electrically conductive membranes 2601, which results in the desired audio frequency of the electrically conductive membrane pump/transducer 2600. I.e., the frequency of the mechanical deflections of the electrically conductive membranes 2601 equal the frequency of the mechanical deflections of membrane 2602, which in turn equals the desired audio frequency.
Benefits of electrically conductive membrane pump/transducer 2600 include that it produces on the order of 100 times more audio power than the electrically conductive membrane array does alone. This gain stems in part from the fact that audio power increases (for a fixed frequency and percent displacement of a given membrane) as the 5th power of membrane diameter, whereas the air volume required to move the large membrane 2602 increases as just the cube of membrane diameter. I.e., a given displaced air volume from the electrically conductive membrane pumps can be put to better use if it is used to move the membrane 2602.
Benefits of electrically conductive membrane pump/transducer 2600 also include that membrane 2602 can use very flexible material, like PDMS (since membrane 2602 is moved/driven by pressure changes that do not depend on the mechanical restoration force of membrane 2602) so that the displacement amplitude of membrane 2602 (audio power increases as the cube of membrane displacement) can be much higher than most other materials, including graphene or metals (such as copper). The net result is that this novel type of speaker can be much more compact than traditional (voice coil, etc.) speakers for a given audio power output.
Benefits of electrically conductive membrane pump/transducer 2600 also include that membrane 2602 can be much thinner than the cone of a voice coil because it is being moved by air pressure (which acts evenly on the entire membrane 2602). A thinner membrane means there is less inertia, which in turn means less power to drive/move membrane 2602 (which results in a higher system efficiency).
Benefits of electrically conductive membrane pump/transducer 2600 also include that there is no heavy copper voice coil attached to the larger membrane (as is used in the voice coil speakers in the prior art that presently dominate the commercial speaker market). For the same reasons as discussed above, less inertia (due to the absence of the heavy copper voice coil) leads to higher efficiency. A related benefit is no resistive heating losses of a copper voice coil (since no voice coil is needed).
Furthermore, there are a few reasons it is not practical to move membrane 2602 directly with an electrostatic force. First, the voltages would be too high, i.e., it would take several thousand volts to significantly move membrane 2602 that is just a few centimeters in diameter. Even if several thousand volts were available, it would likely cause an electrical arc within the air chamber. Second, it is difficult to make strong yet flexible membranes (such as graphene membranes) that are much larger than 1 mm in diameter. Third, it is difficult to drive membrane 2602 directly as it is likely to go into a runaway condition at high voltage and crash against the driving electrode. These limitations are overcome by using the air pressure of the electrically conductive membranes 2601 to mechanically move membrane 2602. While other membranes, such as metal-polymer composite membranes, graphene membranes, graphene oxide membranes and graphene/graphene oxide membranes can alternatively be used, graphene-polymer membranes are generally used for the electrically conductive membranes 2601 because of the low gate voltages and because the array of small electrically conductive membrane pumps operate below the arcing threshold and membrane runaway is minimized.
Although FIG. 26 depicts electrically conductive membranes 2601 and membrane 2602 moving above and below their respective relaxed positions (as shown by curves 2601a and 2601b for electrically conductive membranes 2601 and curves 2602a and 2602b for membrane 2602), electrically conductive membrane pump/transducer 2600 will also work (though it will produce less audio power) if each of electrically conductive membranes 2601 and membrane 2602 moves in one direction only (for example, upward in FIG. 26 as shown by curves 2601a and 2602a, respectively).
While embodiments of the invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the spirit and teachings of the invention. 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. For example, both the small electrically conductive membranes and the larger membrane could be trough-shaped instead of round. In addition, there could be more than one larger membrane. 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, that scope including all equivalents of the subject matter of the claims.
The disclosures of all patents, patent applications, and publications cited herein are hereby incorporated herein by reference in their entirety, to the extent that they provide exemplary, procedural, or other details supplementary to those set forth herein.
Patent Grant
9264796
