US20170367215A1 - Cooling systems and synthetic jets configured to harvest energy and vehicles including the same - Google Patents

Abstract

A cooling system includes a diaphragm, at least one conductor layer disposed on the diaphragm, at least one dielectric film layer, and a controller. The controller is programmed to operate the cooling system in a contact mode and in a non-contact mode. In the contact mode, the diaphragm is controlled to oscillate at a first amplitude such that the conductor layer contacts the dielectric film layer. In the non-contact mode, the diaphragm is controlled to oscillate at a second amplitude such that the conductor layer does not contact the dielectric film layer while the diaphragm oscillates.

Description

TECHNICAL FIELD
• The present specification generally relates to cooling systems and, more particularly, to cooling systems that employ triboelectric devices for energy generation.
BACKGROUND
• Power electronics devices are often utilized in high-power electrical applications, such as inverter systems for hybrid electric vehicles and electric vehicles. Power semiconductor devices, such as insulated gate bipolar transistors (IGBTs) and power transistors, for example, may be thermally coupled to a cooling device (e.g., a heat spreader and/or a heat sink), to remove non-uniform heat fluxes generated by the power semiconductor devices. Operation of the power semiconductor devices may generate high thermal loads. Power semiconductor devices are demanding increased thermal management performance of cooling devices.
• In some cooling devices, a cooling fluid may be used to receive heat from a heat generating device, such as a power semiconductor device, through convective heat transfer and remove the heat from the heat generating device. For example, one device that may be utilized to cool a power semi-conductor device is a synthetic jet device. Generally, a synthetic jet device utilizes an oscillating diaphragm to create an airflow to cool a device. However, the synthetic jet device may generate kinetic energy that is wasted.
• Accordingly, a need exists for alternative cooling systems for electronic device assemblies that harvest kinetic energy.
SUMMARY
• In one embodiment, a cooling system includes a diaphragm, at least one conductor layer disposed on the diaphragm, at least one dielectric film layer, and a controller. The controller is programmed to operate the cooling system in a contact mode and in a non-contact mode. In the contact mode, the diaphragm is controlled to oscillate at a first amplitude such that the conductor layer contacts the dielectric film layer. In the non-contact mode, the diaphragm is controlled to oscillate at a second amplitude such that the conductor layer does not contact the dielectric film layer while the diaphragm oscillates.
• In another embodiment, a synthetic jet device includes a diaphragm, at least one conductor layer disposed on the diaphragm, at least one dielectric film layer, and a controller. The controller is programmed to operate the synthetic jet device in a contact mode and in a non-contact mode. In the contact mode, the diaphragm is controlled to oscillate at a first amplitude such that the conductor layer contacts the dielectric film layer. In the non-contact mode, the diaphragm is controlled to oscillate at a second amplitude such that the conductor layer does not contact the dielectric film layer while the diaphragm oscillates. The oscillation of the diaphragm generates a fluid jet.
• In yet another embodiment, a vehicle includes an electric motor; and a synthetic jet device electrically coupled to the electric motor. The synthetic jet device includes a diaphragm; at least one conductor layer disposed on the diaphragm; at least one dielectric film layer; and a controller. The controller is programmed to operate the synthetic jet device in a contact mode to operate the synthetic jet device in a non-contact mode. In the contact mode, the diaphragm is controlled to oscillate at a first amplitude such that the at least one conductor layer contacts the at least one dielectric film layer. In the non-contact mode, the diaphragm is controlled to oscillate at a second amplitude such that the at least one conductor layer does not contact the at least one dielectric film layer while the diaphragm oscillates.
• These and additional features provided by the embodiments described herein will be more fully understood in view of the following detailed description, in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
• The embodiments set forth in the drawings are illustrative and exemplary in nature and not intended to limit the subject matter defined by the claims. The following detailed description of the illustrative embodiments can be understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:
• FIG. 1 schematically depicts an example cooling system including an oscillating diaphragm according to one or more embodiments described and illustrated herein;
• FIG. 2 schematically depicts an example triboelectric device for use in the cooling system ofFIG. 1 according to one or more embodiments described and illustrated herein;
• FIGS. 3A and 3B schematically depict an example triboelectric device operating in contact mode according to one or more embodiments described and illustrated herein;
• FIGS. 4A and 4B schematically depict an example triboelectric device operating in non-contact mode according to one or more embodiments described and illustrated herein;
• FIG. 5 is a graph illustrating the open-circuit voltage (V_OC) output of the triboelectric device according to one or more embodiments described and illustrated herein;
• FIG. 6 is a graph illustrating the short-circuit current (I_SC) output of the triboelectric device according to one or more embodiments described and illustrated herein; and
• FIG. 7 schematically depicts a perspective view of a vehicle including an electric motor and a power electronics module having the cooling system according to one or more embodiments described and illustrated herein.
DETAILED DESCRIPTION
• Embodiments of the present disclosure are directed to cooling systems including a diaphragm that are operable to harvest electrical energy from the kinetic energy of the oscillating diaphragm. Particularly, embodiments described herein include a diaphragm and a controller programmed to operate the cooling system in a contact mode and a non-contact mode. For example, the controller may be programmed to operate the cooling system in a contact mode in which the diaphragm is controlled to oscillate at a first amplitude such that a conductor layer disposed on the diaphragm contacts a dielectric film layer. In the non-contact mode, the diaphragm is controlled to oscillate at a second amplitude such that the conductor layer does not contact the dielectric film layer when the diaphragm oscillates. As the diaphragm oscillates, energy produced as a result of the triboelectric effect and electrostatic induction between the conductor layer and a dielectric film may be harvested. The harvested energy may be used, for example, to power the cooling system or another electronic device, or may be stored for later use. As an example and not a limitation, the power output may be about 1.5 W/m²when the device operates in non-contact mode and about 2 W/m²when the device operates in contact mode. Various embodiments of cooling systems including triboelectric devices and vehicles incorporating the same are described in detail below.
• FIG. 1 depicts anexample cooling system100. In general, thecooling system100 includes asynthetic jet device102 and one or moreheat generating elements104. Thesynthetic jet device102 includes adiaphragm202 betweenwalls105 of thesynthetic jet device102 that define a fluid housing. In particular, thewalls105 are spaced apart to definecavity106 in which thediaphragm202 is positioned.
• Thediaphragm202 may be formed from a metal, plastic, glass ceramic, elastomeric material, or any other suitable material. Suitable metals include materials such as nickel, aluminum, copper and molybdenum, and alloys such as stainless steel, brass, or the like. Suitable elastomeric materials include, by way of example and not limitation, silicones, rubbers, urethanes, elastic polymers, and the like.
• In various embodiments, thediaphragm202 is coupled to anactuator108 to enable displacement of thediaphragm202 within thecavity106. Theactuator108 may be, for example, a piezoelectric actuator, an electric actuator, an ultrasonic actuator, an electro-restrictive actuator, a pneumatic actuator, or a magnetic actuator. As shown inFIG. 1, theactuator108 is driven by acontroller110.
• Thecontroller110 may be configured as any processing or computing device capable of receiving one or more signals and producing one or more output signals to operate thecooling system100, and more specifically, thesynthetic jet device102. Example processing or computing devices for thecontroller110 include, but are not limited to, programmable logic controllers, analog to digital converter devices, digital to analog converter devices, general purpose microcontrollers, application specific integrated circuits, discrete electronic components, and general purpose computing devices. The functionality of thecontroller110 may be provided by any combination of software, hardware and firmware. In some embodiments, thecontroller110 may include a non-transitory computer-readable medium storing instructions to receive the one or more signals and produce the one or more output signals.
• Thecontroller110 is operable to operate thesynthetic jet device102 in a contact mode and in a non-contact mode. More particularly, thecontroller110 is programmed to oscillate thediaphragm202, such as through theactuator108, at a first amplitude corresponding to the contact mode and a second amplitude corresponding to the non-contact mode. Thecontroller110, and its use to operate thesynthetic jet device102, will be discussed in greater detail hereinbelow.
• In operation, thecontroller110 drives theactuator108 to oscillate thediaphragm202 within thecavity106 of thesynthetic jet device102. As thediaphragm202 oscillates within thecavity106, it displaces fluid in thecavity106, which is expelled from thesynthetic jet device102 through anozzle112 to form afluid jet114. The fluid may be air, another gas, or even a liquid. Thefluid jet114 passes over theheat generating elements104. Through convection, thefluid jet114 facilitates a reduction of the temperature of theheat generating elements104.
• In various embodiments, energy resulting from the oscillation of thediaphragm202 within thecavity106 may be harvested, such as through the use of a capacitor or battery. Accordingly, in various embodiments, thediaphragm202 and at least one of thewalls105 of thesynthetic jet device102 form atriboelectric device200.
• FIG. 2 schematically illustrates an exampletriboelectric device200 in accordance with various embodiments described herein. As shown inFIG. 2, thetriboelectric device200 generally includes thediaphragm202, at least oneconductor layer204 disposed on thediaphragm202, and at least onedielectric film layer206. In the embodiment depicted inFIG. 2, thedielectric film layer206 is disposed on asecond conductor layer208 which is, in turn, disposed on acover210. In various embodiments, thecover210 may be a part of thesynthetic jet device102, such as thewall105. Although the embodiment inFIG. 2 is depicted as including conductor layers204 on opposing surfaces of thediaphragm202, it should be understood that in some embodiments, such as the embodiment depicted inFIG. 1, aconductor layer204 may be disposed on a single surface of thediaphragm202.
• Theconductor layer204 and thesecond conductor layer208 serve as electrodes. Accordingly, the conductor layers208,208 may be made of aluminum, copper, gold, or another conductive material having a triboelectric series rating indicating a propensity to lose electrons. The conductor layers204,208 may be, for example, a thin film of a conductive material. Some suitable materials for the conductor layers204,208 include, by way of example and not limitation, gold thin films and aluminum foil. In various embodiments, eachconductor layer204,208 is made of a material that is at a different position on a triboelectric series than thedielectric film layer206. Moreover, theconductor layer204 may be the same material or a different material as the material of thesecond conductor layer208.
• Thedielectric film layer206 may be made of one or more polymeric materials or another material with a triboelectric series rating indicating a propensity to gain electrons. Thedielectric film layer206 may be, by way of example and not limitation, polyvinyl chloride (PVC), polyimide, a polymeric organosilicon compound, such as polydimethylsiloxane (PDMS), or a fluorinated ethylene polymer, such as fluorinated ethylene propylene (FEP), polytetrafluorotethylene (PTFE), and the like. Although depicted inFIG. 2 as being disposed on theconductor layer208, it is contemplated that in some embodiments, thedielectric film layer206 may be disposed on theconductor layer204 rather than thesecond conductor layer208.
• FIG. 2 also depicts aload212 coupling theconductor layer204 to thesecond conductor layer208. Theload212 may be, by way of example and not limitation, any component suitable to consume or store electric power generated between theconductor layer204 and thesecond conductor layer208. As non-limiting examples, theload212 may be a capacitor, a powered electronic device, such as a sensor or a light-emitting diode (LED), or even a component of thecooling system100, such as thecontroller110. In embodiments in which thecooling system100 consumes the power generated between the conductor layers204 and208, thecooling system100 may be referred to as a self-powered cooling system. In order to generate electricity, thecontroller110 is programmed to operate thesynthetic jet device102 in a contact mode and in a non-contact mode, which will be discussed in turn.
• When thecontroller110 operates thesynthetic jet device102 in contact mode, thediaphragm202 is controlled to oscillate at a first amplitude A₁such that theconductor layer204 contacts thedielectric film layer206, as shown inFIGS. 3A and 3B. In various embodiments, as a non-limiting example, the first amplitude A₁is between about 1 mm and about 5 mm, depending on the space between theconductor layer204 and thedielectric film layer206 and the thickness of theconductor layer204 and thediaphragm202. Without being bound by theory, when theconductor layer204 contacts thedielectric film layer206, the triboelectric effect causes electrons to be transferred from the surface of theconductor layer204 to thedielectric film layer206, thereby causing a net negative charge in thedielectric film layer206 and a net positive charge in theconductor layer204. As a result of the net positive charge in theconductor layer204, electrons flow from theconductor layer208 to theconductor layer204 through theload212.
• The electric field generated by the separated surface charges between theconductor layer204 and thedielectric film layer206 will then give rise to a much higher potential on theconductor layer204 than on thesecond conductor layer208. Such a potential difference will drive the flow of positive charges from theconductor layer204 to thesecond conductor layer208 through theload212 until the potential difference is fully offset by the transferred charges. As a non-limiting example, thesynthetic jet device102 generates energy in an amount of between about 1.0 W/m²and about 3.0 W/m², between about 1.5 W/m²and about 2.5 W/m², or between about 1.75 W/m²and about 2.25 W/m²when operated in contact mode. In another non-limiting example, thesynthetic jet device102 generates about 2 W/m²in contact mode.
• FIGS. 4A and 4B schematically illustrate operation of thesynthetic jet device102 in non-contact mode. When thecontroller110 operates thesynthetic jet device102 in non-contact mode, thediaphragm202 is controlled to oscillate at a second amplitude A₂such that theconductor layer204 does not contact thedielectric film layer206 while thediaphragm202 oscillates. As shown inFIGS. 4A and 4B, when thediaphragm202 is oscillated at amplitude A₂, theconductor layer204 is spaced apart from thedielectric film layer206 by a distance s. As a non-limiting example, the second amplitude A₂is between about 0.5 mm and about 4.5 mm, between about 1 mm and about 4.25 mm, or between about 2 mm and about 4 mm. The distance s may, in some embodiments, be between about 0.05 mm and about 2 mm. The second amplitude A₂is less than the first amplitude A₁and greater than zero (i.e., A₁>A₂>0). Without being bound by theory, when theconductor layer204 is brought into close proximity to (but not contact with) thedielectric film layer206, the electrostatic field between the conductor layer204 (which has a net positive charge) and the dielectric film layer206 (which has a net negative charge) causes thedielectric film layer206 to become slightly polarized, which drives the flow of positive charges from theconductor layer204 to thesecond conductor layer208 through theload212.
• As non-limiting examples, thesynthetic jet device102 generates energy in an amount of between about 0.5 W/m²and about 2.5 W/m², between about 1.0 W/m²and about 2.0 W/m², or between about 1.25 W/m²and about 1.75 W/m²when operated in non-contact mode. In one particular embodiment, thesynthetic jet device102 generates about 1.5 W/m²in non-contact mode.
• In operation, thecontroller110 is programmed to operate thesynthetic jet device102 in a non-contact mode for a number of cycles following operation of thesynthetic jet device102 in a contact mode for a predetermined number of cycles. For example, thecontroller110 may operate thesynthetic jet device102 in a contact mode for one or more cycles, which brings theconductor layer204 and thedielectric film layer206 into contact with one another, producing triboelectric charges through the transfer of electrons. The predetermined number of cycles for operation of thecooling system100 may be any number such as, without limitation, 5 cycles, 3 cycles, or even one cycle.
• In one particular embodiment, the charge imbalance resulting from one cycle of thesynthetic jet device102 in contact mode yields an initial charge imbalance between theconductor layer204 and thedielectric film layer206. As used herein, the “initial charge imbalance” is the charge imbalance that results from the transfer of electrons from theconductor layer204 to thedielectric film layer206 when the two layers contact one another when thesynthetic jet device102 is operated in contact mode. In some embodiments, the initial charge imbalance is achieved as a result of a single contact between theconductor layer204 and thedielectric film layer206 and is a value corresponding to the charge imbalance resulting from separation of theconductor layer204 from thedielectric film layer206. In other embodiments, when thesynthetic jet device102 is operated in contact mode for more than one cycle in a row, the “initial charge imbalance” is the maximum charge imbalance that results during operation in contact mode. For example, the charge imbalance may increase with each contact to a maximum charge imbalance before thesynthetic jet device102 is operated in non-contact mode. The maximum charge imbalance corresponds to the initial charge imbalance for the system. Accordingly, in various embodiments, thecontroller110 is programmed to operate thesynthetic jet device102 in contact mode effective to increase an existing charge balance between theconductor layer204 and thedielectric layer206 to the initial charge imbalance.
• As non-limiting examples, the initial charge imbalance may be between about 10 μC/m²and about 100 μC/m², between about 25 μC/m²and about 75 μC/m², or between about 40 μC/m²and about 60 μC/m². In one particular embodiment, the initial charge imbalance is about 50 μC/m².
• After operating in the contact mode for the predetermined number of cycles, thecontroller110 may be programmed to then switch thesynthetic jet device102 to operation in a non-contact mode. Thecontroller110 may be programmed to operate thesynthetic jet device102 in non-contact mode for more than one cycle before operating thesynthetic jet device102 in contact mode again.
• In some embodiments, thecontroller110 is programmed to operate thesynthetic jet device102 in contact mode responsive to determining that the existing charge imbalance between theconductor layer204 and thedielectric film layer206 is below a threshold charge imbalance. The threshold charge imbalance may be, by way of example and not limitation, about 75% of the initial charge imbalance, about 60% of the initial charge imbalance, about 50% of the initial charge imbalance, or even about 40% of the initial charge imbalance. Accordingly, thecontroller110 may receive charge imbalance information, compare the received charge imbalance information corresponding to an existing charge imbalance to a threshold charge imbalance stored in the memory of thecontroller110, and, when the existing charge imbalance is below the threshold charge imbalance, operate thesynthetic jet device102 in contact mode. For example, in one non-limiting example, thecontroller110 may measure the voltage across the load to obtain the charge imbalance information. However, it is contemplated that thecontroller110 may be configured to receive charge imbalance information in any suitable way.
• In some other embodiments, thecontroller110 may be programmed to operate thesynthetic jet device102 in contact mode responsive to determining that a predetermined amount of time has passed since thesynthetic jet device102 was last operated in contact mode. For example, thecontroller110 may operate thesynthetic jet device102 in contact mode for a predetermined number of cycles (e.g., the diaphragm is oscillated at the first amplitude A₁such that the eachconductor layer204 contacts each correspondingdielectric film layer206 once) and record a time that corresponds to that contact. The time may be, for example, recorded in the memory of thecontroller110. Following the operation in contact mode, thecontroller110 may operate thesynthetic jet device102 in non-contact mode until a predetermined period of time has passed. The predetermined period of time may be, by way of example and not limitation, 3 hours, 6 hours, 12 hours, 18 hours, 24 hours, 36 hours, or even 48 hours. When the predetermined amount of time has passed, thecontroller110 may operate thesynthetic jet device102 in contact mode and record the time that a new contact between theconductor layer204 and thedielectric film layer206 occurs.
• In various embodiments, the operation of thesynthetic jet device102 in non-contact mode enables thesynthetic jet device102 to produce fluid jets while energy produced as a result of the triboelectric effect and electrostatic induction is harvested without adversely impacting thecooling system100, and thesynthetic jet device102, in particular. Accordingly, by programming thecontroller110 to operate thesynthetic jet device102 in a contact mode and a non-contact mode, device durability can be improved because of the lack of contact between thedielectric film layer206 and the conductor layer24 during non-contact operation.
• In one experimental example, acooling system100 included asynthetic jet device200 in which aconductor layer204 in the form of aluminum foil was adhered to the diaphragm and adielectric film layer206 in the form of fluorinate ethylene polymer was used as a contact surface with a deposited gold thin film layer as thesecond conductor layer208 was adhered onto the inner surface of theupper wall105.Conductor layer204 and thedielectric film layer206 were sized and aligned to have a contacting surface area of about 7 cm².FIG. 5 is a plot illustrating the open-circuit voltage (V_OC) during the operation of the device in non-contact mode.FIG. 6 is a plot illustrating the short-circuit current (I_SC) during the operation of the device in non-contact mode.
• As shown inFIGS. 5 and 6, the peaks of the V_OCand the I_SCwere up to about 40 V and about 3 μA, respectively, corresponding to a peak power density of about 0.2 W/m². In the experiment, the energy was able to simultaneously light up ten light-emitting diode (LED) bulbs continuously. Accordingly, the harvested energy may be used to power electronics devices, such as LEDs, sensors, and the like. Alternatively or in addition, the harvested energy may be used to at least partially power thecooling system100, resulting in a self-powered cooling system.
• As stated above, thesynthetic jet devices102 described herein may be incorporated into larger power circuits, such as inverter and/or converter circuits of an electrified vehicle, for example. The electrified vehicle may be a hybrid vehicle, a plug-in electric hybrid vehicle, an electric vehicle, or any vehicle that utilizes an electric motor. Referring now toFIG. 7, avehicle700 configured as a hybrid vehicle or a plug-in hybrid vehicle is schematically illustrated. The vehicle generally comprises agasoline engine770 and anelectric motor772, both of which are configured to provide rotational movement to thewheels780 of thevehicle700 to propel thevehicle700 down the road. Apower circuit702 is electrically coupled to electric motor772 (e.g., by conductors778). Thepower circuit702 may be configured as an inverter and/or a converter circuit that provides electrical power to theelectric motor772. Thepower circuit702 may in turn be electrically coupled to a power source, such as a battery pack774 (e.g., by conductors776). Thepower circuit702 includes one or more cooling systems100 (seeFIG. 1) that include one or moretriboelectric devices200. When thesynthetic jet devices102 of the one ormore cooling systems100 operate, electricity may be harvested and stored or used by one or more components in thevehicle700, such as sensors, LEDs, or other electronic power devices.
• It should now be understood that embodiments of the present disclosure are directed to cooling systems employing synthetic jet devices from which energy may be harvested. A controller is used to operate the synthetic jet device in a contact mode and a non-contact mode to improve durability of the synthetic jet device. During operation in contact mode, a diaphragm of the synthetic jet device is oscillated at an amplitude such that a conductor layer coupled to the diaphragm contacts a dielectric film layer within the synthetic jet device to generate a charge imbalance. During operation in non-contact mode, the diaphragm is oscillated at a second amplitude such that the conductor layer and the dielectric film layer do not contact one another. Although the conductor layer and the dielectric film layer do not contact one another, the charge imbalance generated during operation in contact mode is sufficient to generate electricity as the two are brought close to one another.
• It is noted that the term “approximately” may be utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. Such terms are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue.
• While particular embodiments have been illustrated and described herein, it should be understood that various other changes and modifications may be made without departing from the spirit and scope of the claimed subject matter. Moreover, although various aspects of the claimed subject matter have been described herein, such aspects need not be utilized in combination. It is therefore intended that the appended claims cover all such changes and modifications that are within the scope of the claimed subject matter.

Claims (20)

1. A cooling system comprising:

a diaphragm;

at least one conductor layer disposed on the diaphragm;

at least one dielectric film layer; and

a controller programmed to:

operate the cooling system in a contact mode, wherein the diaphragm is controlled to oscillate at a first amplitude such that the at least one conductor layer contacts the at least one dielectric film layer, and

operate the cooling system in a non-contact mode, wherein the diaphragm is controlled to oscillate at a second amplitude such that the at least one conductor layer does not contact the at least one dielectric film layer while the diaphragm oscillates.

2. The cooling system ofclaim 1, wherein the controller is programmed to operate the cooling system in the non-contact mode for more than one cycle following operation of the cooling system in the contact mode for a predetermined number of cycles.

3. The cooling system ofclaim 1, wherein the controller is programmed to operate the cooling system in the contact mode effective to increase an existing charge imbalance between the at least one conductor layer and the at least one dielectric film layer to an initial charge imbalance.

4. The cooling system ofclaim 3, wherein the controller is programmed to operate the cooling system in the contact mode responsive to determining that the existing charge imbalance between the at least one conductor layer and the at least one dielectric film layer is below about 50% of the initial charge imbalance.

5. The cooling system ofclaim 1, wherein the cooling system generates energy used to power the cooling system.

6. The cooling system ofclaim 1, wherein the second amplitude is less than the first amplitude and greater than 0 mm.

7. The cooling system ofclaim 1, wherein the at least one dielectric layer comprises fluorinated ethylene polymer.

8. The cooling system ofclaim 1, wherein the at least one conductor layer comprises a thin film of gold, copper, or aluminum.

9. A synthetic jet device comprising:

a diaphragm;

at least one conductor layer disposed on the diaphragm;

at least one dielectric film layer; and

a controller programmed to:

operate the synthetic jet device in a contact mode, wherein the diaphragm is controlled to oscillate at a first amplitude such that the at least one conductor layer contacts the at least one dielectric film layer, and

operate the synthetic jet device in a non-contact mode, wherein the diaphragm is controlled to oscillate at a second amplitude such that the at least one conductor layer does not contact the at least one dielectric film layer while the diaphragm oscillates;

wherein the oscillation of the diaphragm generates a fluid jet.

10. The synthetic jet device ofclaim 9, wherein the at least one dielectric film layer comprises one or more polymeric materials.

11. The synthetic jet device ofclaim 10, wherein the one or more polymeric materials comprise fluorinated ethylene polymer.

12. The synthetic jet device ofclaim 9, wherein the at least one conductor layer comprises a thin film of gold, copper, or aluminum.

13. The synthetic jet device ofclaim 9, wherein the controller is programmed to operate the synthetic jet device in the non-contact mode for more than one cycle following operation of the synthetic jet device in the contact mode for a predetermined number of cycles.

14. The synthetic jet device ofclaim 9, wherein the controller is programmed to operate the synthetic jet device in the contact mode effective to increase an existing charge imbalance between the at least one conductor layer and the at least one dielectric film layer to an initial charge imbalance.

15. The synthetic jet device ofclaim 14, wherein the controller is programmed to operate a synthetic jet device in the contact mode responsive to determining that the existing charge imbalance between the at least one conductor layer and the at least one dielectric film layer is below about 50% of the initial charge imbalance.

16. The synthetic jet device ofclaim 9, wherein the synthetic jet device generates energy in an amount between about 0.1 W/m²and about 1.9 W/m²when operated in non-contact mode.

17. The synthetic jet device ofclaim 7, wherein the second amplitude is less than the first amplitude and greater than 0 mm.

18. A vehicle comprising:

an electric motor; and

a synthetic jet device electrically coupled to the electric motor, the synthetic jet device comprising:

a diaphragm;

at least one conductor layer disposed on the diaphragm;

at least one dielectric film layer; and

a controller programmed to:

operate the synthetic jet device in a contact mode, wherein the diaphragm is controlled to oscillate at a first amplitude such that the at least one conductor layer contacts the at least one dielectric film layer, and

operate the synthetic jet device in a non-contact mode, wherein the diaphragm is controlled to oscillate at a second amplitude such that the at least one conductor layer does not contact the at least one dielectric film layer while the diaphragm oscillates.

19. The vehicle ofclaim 18, wherein the controller is programmed to operate the synthetic jet device in the contact mode responsive to determining that an existing charge imbalance between the at least one conductor layer and the at least one dielectric film layer is below about 50% of an initial charge imbalance.

20. The vehicle ofclaim 18, wherein the synthetic jet device is at least partially powered by electricity produced by the oscillation of the diaphragm.

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