Electroactive polymer generators

• US 20060238066A1
• Filed: 01/24/2006
• Published: 10/26/2006
• Est. Priority Date: 07/20/1999
• Status: Active Grant

• Current Assignee: SRI International, Inc.
• Original Assignee: SRI International, Inc.
• Inventors: Kornbluh, Roy D., Pelrine, Ronald E., Garcia, Pablo E., Eckerle, Joseph Stephen
• Granted Patent: US 7,368,862 B2
• Time in Patent Office: Days
• US Class Current: 310/309
• CPC Class Codes: F02G 1/043 the engine being operated by expansion and contraction of a mass of working gas which is heated and cooled in one of a plurality of constantly communicating expansible chambers, e.g. Stirling cycle type engines
• CPC Class Codes: F02G 2243/52 acoustic
• CPC Class Codes: F04B 35/00 Piston pumps specially adapted for elastic fluids and characterised by the driving means to their working members, or by combination with, or adaptation to, specific driving engines or motors, not otherwise provided for
• CPC Class Codes: F04B 35/045 using solenoids
• CPC Class Codes: F04B 43/043 Micropumps
• CPC Class Codes: F05C 2225/08 Thermoplastics
• CPC Class Codes: F25B 9/14 characterised by the cycle used, e.g. Stirling cycle
• CPC Class Codes: H02N 11/006 Motors
• CPC Class Codes: H02N 2/023 Inchworm motors
• CPC Class Codes: H04R 19/02 Loudspeakers H04R19/01 takes precedence
• CPC Class Codes: H04R 23/00 Transducers other than those covered by groups H04R9/00 - H04R21/00 diaphragms for transducers of the distributed-mode type H04R7/045
• CPC Class Codes: H10N 30/2042 Cantilevers, i.e. having one fixed end
• CPC Class Codes: H10N 30/2047 Membrane type
• CPC Class Codes: H10N 30/206 using only longitudinal or thickness displacement, e.g. d33 or d31 type devices
• CPC Class Codes: H10N 30/308 Membrane type
• CPC Class Codes: H10N 30/857 Macromolecular compositions
• CPC Class Codes: Y10S 310/80 Piezoelectric polymers, e.g. PVDF

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.

Claims

1. A method of converting mechanical energy to electrical energy using an electroactive polymer transducer that includes an electroactive polymer and two electrodes, the method comprising:

mechanically deflecting the electroactive polymer transducer to have a larger area between the electrodes than an area between the electrodes before the deflection;

applying a voltage difference between the two electrodes;

mechanically contracting the electroactive polymer transducer to have a smaller area between the electrodes than the area between the electrodes when the voltage difference was applied; and

removing electrical energy using the two electrodes.

2. The method of claim 1 wherein the voltage difference applied between the two electrodes is not large enough to cause the electroactive polymer to mechanically deflect.

3. The method of claim 1 wherein electrostatic forces, resulting from the voltage difference applied between the two electrodes, are insufficient to balance elastic restoring forces of the deflection.

4. The method of claim 1 wherein the area between the electrodes before the mechanical deflection occurs in a resting position of the transducer that has no external electrical or mechanical input applied to the polymer.

5. The method of claim 4 wherein the resting position includes pre-strain in the polymer.

6. The method of claim 5 wherein the polymer is pre-strained by a factor in the range of about 1.5 to about 50 times an original area of the polymer prior to the pre-strain.

7. The method of claim 5 wherein the polymer comprises pre-strain in a first direction that improves energy conversion in a second direction.

8. The method of claim 1 wherein the contraction separates the electrodes and raises electrical energy of the voltage difference on the electrodes.

9. The method of claim 1 wherein a like charge within each electrode compresses during the contraction, which raises electrical energy of the charge.

10. The method of claim 1 wherein the electrical energy is removed using an electronic circuit in electrical communication with the electrodes.

11. The method of claim 1 wherein the electrical energy is removed from the electrodes when the electroactive polymer transducer has fully contracted.

12. The method of claim 1 wherein electrical energy is removed from the electrodes during contraction of the electroactive polymer transducer.

13. The method of claim 1 wherein the polymer is capable of a maximum linear strain of at least about 50 percent.

14. The method of claim 1 wherein the mechanically contraction at least partially results from elastic return of the electroactive polymer.

15. The method of claim 1 wherein the contraction is a contraction in one direction of a plane of the electroactive polymer.

16. The method of claim 1 wherein the electroactive polymer has a substantially constant thickness before deflection and the deflection comprises a decrease in the substantially constant thickness.

17. The method of claim 1 wherein the electroactive polymer has an elastic modulus at most about 100 MPa.

18. A method of converting mechanical energy to electrical energy using an electroactive polymer transducer that includes an electroactive polymer and two electrodes on opposite surfaces of the polymer, the method comprising:

mechanically stretching the electroactive polymer transducer to have a larger area between the electrodes than an area between the electrodes before the stretch;

applying a voltage difference between the two electrodes while the polymer is stretched;

mechanically contracting the electroactive polymer transducer to have a smaller area between the electrodes than the area between the electrodes when the voltage difference was applied; and

removing electrical energy using the two electrodes.

19. The method of claim 18 wherein electrostatic forces, resulting from the voltage difference applied between the two electrodes, are insufficient to balance elastic restoring forces of the stretch.

20. The method of claim 19 wherein a like charge within each electrode compresses during the contraction, which raises electrical energy of the charge.