Abstract: The invention describes rolled electroactive polymer devices. The invention also describes employment of these devices in a wide array of applications and methods for their fabrication. A rolled electroactive polymer device converts between electrical and mechanical energy; and includes a rolled electroactive polymer and at least two electrodes to provide the mechanical/electrical energy conversion. Prestrain is typically applied to the polymer. In one embodiment, a rolled electroactive polymer device employs a mechanism, such as a spring, that provides a force to prestrain the polymer. Since prestrain improves mechanical/electrical energy conversion for many electroactive polymers, the mechanism thus improves performance of the rolled electroactive polymer device.

Abstract: The invention relates to systems that provide variable stiffness and/or variable damping using an electroactive polymer transducer. Systems described herein offer several techniques that provide variable and controlled stiffness and/or damping. A transducer may be implemented using open loop control, thereby providing simple systems that inactively deliver a desired stiffness and/or damping performance. Alternately, closed loop control techniques permit electroactive polymer transducer designs that actively adapt the stiffness and/or damping performance of a system. Further, transducers may be implemented in a device whose stiffness changes with deflection of the polymer.

Abstract: This disclosure relates to transducers, methods of making transducers and methods of converting between electrical energy and mechanical energy. The transducers comprise an elastomeric film disposed between two electrodes wherein at least one electrode can be a compliant electrode. The elastomeric film comprises a polyphosphazene.

Abstract: The present invention relates to improved devices, systems and methods that convert between electrical and mechanical energy. An electroactive polymer transducer converts between electrical and mechanical energy. An active area is a portion of an electroactive polymer transducer. The active area comprises a portion of an electroactive polymer and at least two electrodes that provide or receive electrical energy to or from the portion. The present invention relates to transducers and devices comprising multiple active areas that are in electrically communication. More specifically, the present invention relates to master/slave arrangements for multiple active areas disposed on one or more electroactive polymers. In a master/slave arrangement, a first active area deflects (a ‘master’), and a second active area reacts (a ‘slave’).

Abstract: An electrostrictive polymer actuator comprises an electrostrictive polymer with a tailorable Poisson's ratio. The electrostrictive polymer is electroded on its upper and lower surfaces and bonded to an upper material layer. The assembly is rolled tightly and capped at its ends. In a membrane structure having a membrane, a supporting frame and a plurality of threads connecting the membrane to the frame, an actuator can be integrated into one or more of the plurality of threads. The electrostrictive polymer actuator displaces along its longitudinal axis, thereby affecting movement of the membrane surface.

Abstract: High performance electromechanical devices suitable for a wide range of applications are described. The electroactive devices are capable of operating in a manner that offers enhanced mechanical displacement responses and increased load-bearing capabilities. In one embodiment, the device is capable of providing a significantly increased level of free displacement. The electroactive devices include an electroactive composite which includes at least one electroactive material that may comprise an electrostrictive or a piezoelectric material and a tensioning device which is adapted for inducing a mechanical pre-load to the electroactive composite structure. The tensioning device exerts a mechanical pre-load upon the electroactive material which alters stress profile, increases mechanical energy and increases stored elastic energy of the electroactive devices.

Abstract: A phase mixed thermoplastic polyurethane elastomer is provided for use in tranducers including underwater transducers, sonars and other electrostriction driven devices. The thermoplastic polyurethane elastomer includes an isocyanate, a butanediol, a polytetramethylene ether glycol, and a polyhydric alcohol.

Abstract: The present invention relates to transducers, their use and fabrication. The transducers convert between mechanical and electrical energy. Some transducers of the present invention include a pre-strained polymer. The pre-strain improves the conversion between electrical and mechanical energy. The present invention also relates to devices including an electroactive polymer to convert between electrical and mechanical energy. The present invention further relates to compliant electrodes that conform to the shape of a polymer included in a transducer. The present invention provides methods for fabricating electromechanical devices including one or more electroactive polymers.

Abstract: The present invention relates to an electro-active device having an electro-active structure extending along a minor axis (36) which is curved, for example in a helix around a major axis (37). The electro-active structure comprises successive electro-active portions (35) extending around said minor axis and arranged with electrodes to bend, when activated, around the minor axis (36) such that bending of the successive portions (35) is concomitant with rotation of the electro-active structure about the minor axis (36) adding incrementally along the minor axis (36). The electro-active structure generates displacement out of the local plane in which the minor axis is curved. The electra-active structure may be continuous electro-active member (35) extending along and curving around the minor axis (35), for example helically to form a helical helix. Alternatively, the electro-active structure may be a plurality of discrete elements (211) connected together.

Abstract: Microactuator comprising a volume changing layer (1) and a carrier substrate layer (2) carrying the volume changing layer (1), the microactuator also comprising a reinforcing structure (3) having an unevenly distributed bending stiffness and that the reinforcing structure (3) is spread over any of the layers (1), (2) to control the movement of the microactuator.

Abstract: The present invention relates to electroactive polymers that are pre-strained to improve conversion from electrical to mechanical energy. When a voltage is applied to electrodes contacting a pre-strained polymer, the polymer deflects. This deflection may be used to do mechanical work. The pre-strain improves the mechanical response of an electroactive polymer. The present invention also relates to actuators including an electroactive polymer and mechanical coupling to convert deflection of the polymer into mechanical work. The present invention further relates to compliant electrodes that conform to the shape of a polymer. The present invention provides methods for fabricating electromechanical devices including one or more electroactive polymers.

Abstract: A piezoelectric device is assembled from a piezofilm sensor enclosed between two layers of a multilayer board with a printed circuit.

Abstract: The present invention relates to transducers, their use and fabrication. The transducers convert between mechanical and electrical energy. Some transducers of the present invention include a pre-strained polymer. The pre-strain improves the conversion between electrical and mechanical energy. The present invention also relates to devices including an electroactive polymer to convert between electrical and mechanical energy. The present invention further relates to compliant electrodes that conform to the shape of a polymer included in a transducer. The present invention provides methods for fabricating electromechanical devices including one or more electroactive polymers.

Abstract: The invention provides sensors that comprise a transducer that converts between mechanical energy and electrical energy. The transducer comprises an electroactive polymer in electrical communication with at least two electrodes. When a relatively small voltage difference is applied between the electrodes, deflection of the polymer results in a measurable change in electrical energy for the transducer. The change in electrical energy may correspond to a change in resistance, capacitance, or a combination thereof. Sensing electronics circuits in electrical communication with electrodes detect the electrical energy change.

Abstract: The present invention relates to mechanical-electrical power conversion systems. The systems comprise one or more electroactive polymers that convert between electrical and mechanical energy. When a voltage is applied to electrodes contacting an electroactive polymer, the polymer deflects. This deflection may be converted into rotation of a power shaft included in a motor. Repeated deflection of the polymer may then produce continuous rotation of the power shaft.

Abstract: The present invention relates to electroactive polymers that are pre-strained to improve conversion from electrical to mechanical energy. When a voltage is applied to electrodes contacting a pre-strained polymer, the polymer deflects. This deflection may be used to do mechanical work. The pre-strain improves the mechanical response of an electroactive polymer. The present invention also relates to actuators including an electroactive polymer and mechanical coupling to convert deflection of the polymer into mechanical work. The present invention further relates to compliant electrodes that conform to the shape of a polymer. The present invention provides methods for fabricating electromechanical devices including one or more electroactive polymers.

Abstract: An ultrasound transducer that includes a piezoelectric film having a first end and a second end, a plurality of electrodes disposed on the piezoelectric film, at least one securing member and a support structure which is generally cylindrical. The first end and the second end of the piezoelectric film are secured to the support structure by at least one securing member.

Abstract: Disclosed generators includes one or more transducers that use electroactive polymer films to convert mechanical energy to electrical energy. The generators may include one or more transmission mechanisms that transfer a portion of an unused biological energy source, an unused environmental energy source or combinations of both to the one or more transducers located in the generators. The energy received by the transducers may be converted to electrical energy by the transducers in conjunction with conditioning electronics located within the generator. A heel-strike generator is disclosed that is integrated into the heel of footwear and is used to convert mechanical energy generated during human bipedal motion to electrical energy.

Abstract: An electromechanic film intended for transforming electric energy into mechanical energy and transforming mechanical energy into electric energy. The film (1) is dielectric and formed of cells (3), the ratio of the height and width of which cells is between 3:1 and 1:3. By joining two such films together and controlling them in such a way that in the first film (1) the electric field strength decreases and in the second film (1) the electric field strength increases, a bending acoustic element is provided.

Abstract: A device for opening and closing an opening (11), in particular in a motor vehicle, by means of a motor-driven, movable part (10), with a control unit (26) and a pinch prevention sensor (14), which is disposed essentially along an edge (20) of the part (10) and/or of a frame profile (12) bordering the opening (11) and which, during the closing of the part (10), detects an obstacle (24) that is in the movement path of the part (10) and sends a signal to the control unit (26) in order to stop or reverse the movement of the part (10), wherein the pinch prevention sensor (14) has a highly elastic, electroactive polymer (EAP) material (30), in particular polyurethane, fluoroelastomer, polybutadiene, fluorosilicone, or silicone, disposed between electrodes (28, 34, 36), which produces a voltage change in the electrodes (28, 34, 36) in the event of a deformation.

Abstract: An underwater acoustic transducer includes a set of formed substrates of piezoelectric polymer composite, the formed substrates having at least a first and second surface. Conductive electrodes are deposited on the first and second sides of the formed substrates. One surface of the substrate is bonded to an acoustically absorptive backing material. Either surface can be made to conform to a singly or doubly curved geometry. Electrodes deposited on these substrates may be continuous to form a single transducer element, or segmented to form sub-arrays of transducer elements.

Abstract: The invention relates to systems and methods for electrically communicating with an electroactive polymer using one or more electrodes that do not contact the polymer. A non-contact electrode communicates charge to or from a portion of the polymer, typically through a medium. For example, the medium may include air, a vacuum, or a specialized gas that facilitates transfer of charge between the electrode and the polymer. The charge may include positive or negative ions or electrodes and may act to actuate the polymer, or diminish actuation applied to polymer in one or more specific polymer portions.

Abstract: The active/passive absorber for extended vibration and sound radiation control includes principally two layers. The first layer has a low stiffness per unit area which allows motion in the direction perpendicular to its main plane. The second layer is principally a mass layer. These two combined layers have a frequency of resonance close to one of the main structure. The dynamic behavior of the coupled system makes the active/passive absorber a passive absorbe; however, the first layer can be electrically actuated to induce motion in the direction perpendicular to its main plane. This addition property induces and/or changes the motion of the mass layer and therefore improves the dynamic properties of the active/passive absorber system.

Abstract: Various piezoelectric transducers are provided. In one form, a polymer film or thin ceramic piezoelectric transducer is formed of various piezoelectric (active) and dielectric (inactive) layers in which the piezoelectric effect may be attenuated locally at any given point on the surface of the transducer, by use of printed circuit patterns, preferably made by photolithography. This provides a practical realization of a distributed piezoelectric transducer with a bi-dimensional polarization profile that varies smoothly over the surface of the piezoelectric structure. Flexibility of the fabrication procedure provides a way to optimize the design of a distributed piezoelectric transducer for applications such as active vibration control. In another form, a segmented piezoelectric transducer includes a set of active elements such as piezofilms, electronics and flexible printed circuits and connected with external electronic circuitry.

Abstract: In a system for supplying power to ROSAR transmitting and receiving antennas that are integrated into the tip of a helicopter rotor blade, wind energy is converted directly into electrical energy locally at the rotor blade tip.

Abstract: The present invention relates to polymers, transducers and devices that convert between electrical and mechanical energy. When a voltage is applied to electrodes contacting an electroactive polymer, the polymer deflects. This deflection may be used to do mechanical work. Similarly, when the electroactive polymer deflects, an electric field is produced in the polymer. This electric field may be used to produce electrical energy. An active area is a portion of a polymer having sufficient electrostatic force to enable deflection of the portion and/or sufficient deflection to enable a change in electrostatic force. The present invention relates to transducers and devices including multiple active areas. The invention also relates to methods for actuating one or more active areas.

Abstract: This present invention provides an array formed by a continous line array of piezoelectric film with discrete points of increased sensitivity to sense and measure acoustic signals. The configuration provided by the present invention simultaneously provides the advantages and attributes of both the continuous line array and the multi-element discrete array. The line array and the multi-element array are designed to enhance or cancel specific frequency bands of signal noise and to enhance beam forming of the array. The piezoelectric array can be extended and shaped into two-dimensional and three-dimensional hydrophone arrays. The present invention comprises a continuous line array formed by a single piece of piezoelectric film with one or more points of enhanced sensitivity to alter the beam pattern or spectral sensitivity of the array. The electrical output of the entire array may be observed with one set of connectors, one positive and one negative lead.

Abstract: This disclosed generators include one or more transducers that use electroactive polymer films to convert thermally generated mechanical energy to electrical energy. The generators may include one or more transmission mechanisms that convert a portion of thermal energy generated from a heat source such as internal combustion, external combustion, solar energy, geothermal energy or waste heat, to mechanical energy that is used to drive the one or more transducers located in the generator. The energy received by the transducers may be converted to electrical energy by the transducers in conjunction with conditioning electronics located within the generator. One embodiment of the present invention provides an energy conversion device with two chambers each chamber including a diaphragm transducer that may convert thermal energy to electricity using a thermodynamic cycle such as a Stirling gas cycle.

Abstract: A piezoelectric transducer apparatus comprises at least one piezoelectric unit and a body structure. Each of the at least one piezoelectric unit has a piezoelectric block and at least one pair of electrodes. Each electrode is adhered to one surface of the piezoelectric block. Each of the at least one piezoelectric unit is adhered to the surface of the body structure with the electrode exposed externally. The transducer apparatus has a generalized sensor equation which can be modeled in a fourth-order partial differential equation mathematical system. At least one of the electrodes or the piezoelectric block of each of the at least one piezoelectric unit has a shape matched to a desired body strain pattern existing in the body structure wherein the electrode of each of the at least one piezoelectric unit may excite a strain pattern in the body structure that is the same as the desired body strain pattern.

Abstract: A method for manufacturing a thin film is performed such that the internal stress is controlled while the preferred orientation property is maintained at a high value. An AlN piezoelectric thin film is formed on a substrate by a sputtering method using a mixed gas including Ar and nitrogen, wherein the mixed gas has a nitrogen flow rate ratio, that is, nitrogen flow rate relative to the sum of the Ar flow rate and the nitrogen flow rate, of about 10% to about 75%.

Abstract: The present invention relates to electroactive polymers that are pre-strained to improve conversion from electrical to mechanical energy. When a voltage is applied to electrodes contacting a pre-strained polymer, the polymer deflects. This deflection may be used to do mechanical work. The pre-strain improves the mechanical response of an electroactive polymer. The present invention also relates to actuators including an electroactive polymer and mechanical coupling to convert deflection of the polymer into mechanical work. The present invention further relates to compliant electrodes that conform to the shape of a polymer. The present invention provides methods for fabricating electromechanical devices including one or more electroactive polymers.

Abstract: A device for providing an electromechanical response includes two polymeric webs bonded to each other along their lengths. At least one polymeric web is activated upon application thereto of an electric field and exhibits electrostriction by rotation of polar graft moieties within the polymeric web. In one embodiment, one of the two polymeric webs in an active web upon application thereto of the electric field, and the other polymeric web is a non-active web upon application thereto of the electric field. In another embodiment, both of the two polymeric webs are capable of being active webs upon application thereto of the electric field. However, these two polymeric webs are alternately activated and non-activated by the electric field.

Abstract: The present invention relates to transducers, their use and fabrication. The transducers convert between mechanical and electrical energy. Some transducers of the present invention include a pre-strained polymer. The pre-strain improves the conversion between electrical and mechanical energy. The present invention also relates to devices including an electroactive polymer to convert between electrical and mechanical energy. The present invention further relates to compliant electrodes that conform to the shape of a polymer included in a transducer. The present invention provides methods for fabricating electromechanical devices including one or more electroactive polymers.

Abstract: A method for producing the piezoelectric thin film is based on a sol-gel process and comprises the steps of: coating a substrate with a sol composition comprising a sol, of a metal component for constituting a piezoelectric film, and a polymer compound and then drying the coating to form a film; pre-sintering the film to form a porous thin film of gel comprising an amorphous metal oxide; pre-annealing the porous thin film of gel to convert the film to a film of a crystalline metal oxide; repeating the steps at least once to form laminated films of a crystalline metal oxide; and annealing the films thus prepared to grow crystal grains of perovskite type in the film into a larger size.

Abstract: The invention described herein supplies a new class of electroactive polymeric blend materials which offer both sensing and actuation dual functionality. The blend comprises two components, one component having a sensing capability and the other component having an actuating capability. These components should be co-processable and coexisting in a phase separated blend system. Specifically, the materials are blends of a sensing component selected from the group consisting of ferroelectric, piezoelectric, pyroelectric and photoelectric polymers and an actuating component that responds to an electric field in terms of dimensional change. Said actuating component includes, but is not limited to, electrostrictive graft elastomers, dielectric electroactive elastomers, liquid crystal electroactive elastomers and field responsive polymeric gels. The sensor functionality and actuation functionality are designed by tailoring the relative fraction of the two components.

Abstract: The present invention relates a manufacturing method for a multilayered piezoelectric/electrostrictive ceramic actuator by a sintering process at low temperature. The present invention makes feasible a high quality image and high speed printing, as large displacement and high speed actuation are feasible because it can get greater displacement and driving speed, even with small variation in driving voltage, because of piezoelectric/electrostrictive layer and upper electrode being alternately heaped to produce a multilayer structure.

Abstract: A miniature piezoelectric transducer element is provided, comprising: (a) a cell element having a cavity; (b) a flexible piezoelectric layer attached to the cell member, the piezoelectric layer having an external surface and an internal surface, the piezoelectric layer featuring such dimensions so as to enable fluctuations thereof at its resonance frequency upon impinging of an external acoustic wave; and (c) a first electrode attached to the external surface and a second electrode attached to the internal surface of the piezoelectric layer. At least one of the electrodes may be specifically shaped so as to provide a maximal electrical output, wherein the electrical output may be current, voltage or power. A preferred shape of the electrodes includes two cores interconnected by a connecting member. The transducer element may function as a transmitter.

Abstract: A method of forming an ultrasound transducer having thermoformed protuberances comprises providing a substrate having a plurality of perforations of a given dimension. The perforations or apertures are formed in the substrate and operate to determine the resonance frequency associated with the transducer. A film of polymeric material capable of showing piezoelectric properties when strained in its plane and electrically biassed by a field applied in a direction normal to its faces, is then laminated onto the substrate. The film is heated to a given temperature and a pressure differential is applied between the top and bottom surfaces of the film for a sufficient time to form protuberances in the film through the apertures in the substrate.

Abstract: A multi-layer piezoelectric transducer includes a first polymeric layer of piezoelectric material having spaced apart first and second surfaces and a second polymeric layer of piezoelectric material having spaced apart first and second surfaces. A first ground layer overlies the first surface of the first polymeric layer and a second ground layer overlies the first surface of the second polymeric layer. A signal layer is sandwiched between the second surfaces of the first and second polymeric layers.

Abstract: A bone conduction microphone and speaker mountable in contact with a user's head or head area, each utilize a strategically mounted audio transducer that is preferably a piezoelectric ceramic bender. In the case of the speaker, the bender is coupled to an audio transformer which may or may not be potted with the bender within the same housing. Additionally, the speaker bender is mounted on a foam layer either with or without a supporting shelf depending on the desired application. The microphone bender is potted within the housing and includes a JFET and resistor mounted directly to the elements of the bender. The present microphone is designed to create the largest possible acoustic mismatch with air while nearly matching the acoustic impedance to the human skill structure. This attenuates the amount of ambient air noise coupled sound receivable into the microphone by greater than 80 dB. The speaker is designed with acoustic impedance matched for bone conduction sound.

Abstract: An electro-acoustic transducer in which a plurality of cymbal-type electro-acoustic actuators are disposed in mechanical and electrical parallel between a pair of stiff plates. The resultant transducer resonates at a lower frequency than the cymbals, with a greater generated force.

Abstract: There is provided an actuator utilizing a piezoelectric transducer that is structured in small size by feeding the electrical power to the internal surface to the piezoelectric transducer formed in the cylindrical shape. The electrodes are formed to both front and rear surfaces of a sheet type piezoelectric element and this element is wound in the cylindrical shape. The cylindrical material is normalized under the predetermined temperature and a voltage is applied across the electrodes for the polarization purpose. An electrode terminal having the contactors is inserted to the internal surface of the piezoelectric transducer formed in the cylindrical shape and the contactors are placed in contact with the electrodes exposed at the internal surface of the cylindrical shape for the purpose of power feeding.

Abstract: A microactuator array with an integrally formed package is disclosed. Because the package is made from the same material and at the same time as the actuator itself, no extra time or cost is associated with packaging. In addition, it is contemplated that the package may be configured to provide all the necessary interconnections and leads for addressing and distributing power to the various layers in the microactuator stack. Thus, no additional steps or cost are associated with electrical interconnection.

Abstract: A multiple transducer array structure comprises a single piezoelectric film material having a plurality of alternately shaped concave and convex regions and responsive to an energy signal incident thereon, the alternating concave and convex regions each having a given radius, each of the regions integrally formed with another of the regions, each of the concave and convex regions vibrating in response to the energy signal with opposite phase to cause the transducer to operate at a given resonant frequency determined by the average radius of the regions. A method of forming the corrugated transducer is also disclosed.

Abstract: An air transducer apparatus comprising a curved piezoelectric film having a first surface and a second surface opposite the first surface, a first electrode layer disposed on at least a portion of the first surface of the film; and a second electrode layer disposed on a portion of the second surface of the film defining the second electrode layer being sized less than the first electrode layer for generating a signal in response to acoustic energy incident on the piezoelectric film.

Abstract: A piezoelectric/electrostrictive device is formed with a connecting plate, a diaphragm, and a substrate which are mutually joined. A joining direction of the connecting plate with the substrate and a joining direction of the connecting plate with the diaphragm are mutually intersected to form a cross. The diaphragm is straddled between the connecting plate and the substrate. A piezoelectric element is arranged on a surface of the diaphragm, and the diaphragm is convexly curved in a direction perpendicular to the two directions forming the cross. The piezoelectric/electrostrictive device is an element for converting electrical energy into mechanical energy such as a mechanical displacement, force or vibrations. Conversely, the piezoelectric/electrostrictive device may be employed to convert mechanical energy into electrical energy, as well as improve the operational characteristics thereof.

Abstract: A transducer apparatus is disclosed having a spool member with a body portion and first and second elevated regions formed on the body portion. A PVDF film surrounds the spool member, the film including an inner surface facing the spool member and an outer surface opposite the inner surface. The film as surrounding the spool member has a predetermined frequency of resonance. Lateral ends of the film are secured together by a securing material. The securing material is such that the secured ends of the film will have substantially the same resonance frequency as a remainder of the film. The film includes a non-electrode area at a perimeter of the inner surface and an electrode material formed on a remainder of the inner surface. Upon securing the lateral edges of the film together, the securement is at overlapping non-electrode lateral edges of the film. The securing material may be any one of an adhesive in combination with screws or thermally deformable nails, adhesive alone, tape, or ultrasonic welding.

Abstract: An ultrasound receiver includes a hollow cylinder formed primarily from flexible piezoeelectric film, the hollow cylinder having an outer surface, an inner surface, a central axis and a height measured parallel to the central axis. A sensing electrode is formed from conductive material applied to the inner surface, while a grounded electrode is formed from conductive material applied to the outer surface. The hollow cylinder is supported by a support structure configured to allow progagation of vibration waves circumferentially around a major part of the hollow cylinder. The sensing electrode is formed as a strip extending in an extensional direction substantially parallel to the central axis along a major part of the height, the strip subtending at the central axis an angle of not more than 90°.

Abstract: A thermally stable, piezoelectric and pyroelectric polymeric substrate was prepared. This thermally stable, piezoelectric and pyroelectric polymeric substrate may be used to prepare electromechanical transducers, thermomechanical transducers, accelerometers, acoustic sensors, infrared sensors, pressure sensors, vibration sensors, impact sensors, in-situ temperature sensors, in-situ stress/strain sensors, micro actuators, switches, adjustable fresnel lenses, speakers, tactile sensors, weather sensors, micro positioners, ultrasonic devices, power generators, tunable reflectors, microphones, and hydrophones. The process for preparing these polymeric substrates includes: providing a polymeric substrate having a softening temperature greater than 100° C.

Abstract: An electrical energy generator relying upon piezoelectricity includes electrical generating elements comprising electroded bodies of an electrostrictive material, e.g., polyurethane, having inherent but weak piezoelectric characteristics. A d.c. bias is applied between the electrodes for field-inducing a larger piezoelectric characteristic whereby, upon applying mechanical energy to the element, in known manner, for alternately straining and destraining the body, electrical charge is generated on the electrodes with a high mechanical energy to electrical energy conversion efficiency.