Electroactive polymer transducers and actuators

• US 6,781,284 B1
• Filed: 07/20/2000
• Issued: 08/24/2004
• Est. Priority Date: 02/07/1997
• Status: Expired due to Term

• Current Assignee: SRI International, Inc.
• Original Assignee: SRI International, Inc.
• Inventors: Pelrine, Ronald E., Kornbluh, Roy D., Pei, Qibing
• Primary Examiner(s): Budd, Mark
• Application Number:
  US09/620,025
• Time in Patent Office: 1,496 Days
• Field of Search: 310/800, 310/330, 310/328
• US Class Current: 310/330
• 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: 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 30/206 using only longitudinal or thickness displacement, e.g. d33 or d31 type devices
• CPC Class Codes: H10N 30/857 Macromolecular compositions
• CPC Class Codes: H10N 30/886 Mechanical prestressing means, e.g. springs springs in general F16F1/00
• CPC Class Codes: Y10S 310/80 Piezoelectric polymers, e.g. PVDF

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.

Claims

1. A transducer for converting from electrical energy to mechanical energy, the transducer comprising:

at least two electrodes;

a polymer arranged in a manner which causes a portion of the polymer to deflect from a first position with a first surface area to a second position with a second surface area in response to a change in electric field;

a support structure for securing the portion of the polymer at the first position wherein the portion of the polymer is stretched from an initial surface area to the first surface area to improve the mechanical response of the transducer when it deflects from the first position to the second position and wherein the support structure is for supplying a force to the stretched portion of the polymer that prevents the stretched portion of the polymer from returning from the first surface area to about its initial surface area and wherein a ratio of the first surface area to the initial surface area is in the range of about 1.5 to 50.

2. The transducer of claim 1 wherein the transducer has a maximum linear strain of at least about 50 percent in response to the change in electric field.

3. The transducer of claim 1 wherein the transducer has a maximum linear strain of at least about 100 percent in response to the change in electric field.

4. The transducer of claim 1 wherein the transducer has a maximum area strain of at least about 100 percent in response to the change in electric field.

5. The transducer of claim 1 wherein the pre-strain is applied to a first orthogonal direction at a pre-strain greater than pre-strain in a second orthogonal direction.

8. The transducer of claim 1 wherein the polymer comprises one of a silicone rubber and an acrylic.

9. The transducer of claim 1 wherein the polymer comprises a textured surface.

10. The transducer of claim 1 wherein the polymer has a thickness between about 1 micrometer and 2 millimeters.

11. The transducer of claim 1 wherein tire polymer is one of a commercially available silicone elastomer, polyurethane, PVDF copolymer or adhesive elastomer.

12. The transducer of claim 1 wherein the change in electric field is at most about 440 MegaVolts/meter.

13. The transducer of claim 1 wherein the polymer has a maximum actuation pressure between about 0.1 Pa and about 10 MPa.

14. The transducer of claim 1 wherein the polymer has an operational frequency less than about 100 kHz.

15. The transducer of claim 1 wherein the polymer has an elastic modulus below about 100 MPa.

16. The transducer of claim 1 wherein the portion of the polymer deflects out of the plane of the polymer in response to the change in electric field.

17. The transducer of claim 1 wherein the transducer is included in an artificial muscle.

6. The transducer of clam 5 wherein the pre-strain applied to the first orthogonal direction is used to enhance deflection in the second orthogonal direction.

7. The transducer of claim 6 wherein the polymer has a dielectric constant between about 2 and about 20.

18. A transducer for converting electrical energy to mechanical energy, the transducer comprising:

at least two electrodes; and

a polymer arranged in a manner which causes a portion of the polymer to deflect from a first position with a first length to a second position with a second length in response to a change in electric field provided by the at least two electrodes, wherein the portion deflects with a linear strain between about 50 percent and about 215 percent between the first length and the second in response to the change in electric field during operation of said transducer;

a support structure for securing the polymer during the deflection between the first position and the second position.

19. The transducer of claim 18 wherein the polymer comprises one of a silicone rubber and an acrylic.

20. The transducer of claim 18 wherein the polymer is one of a commercially available silicone elastomer, polyurethane, PVDF copolymer or adhesive elastomer.

21. The transducer of claim 18 wherein the polymer has a dielectric constant between about 2 and about 20.

22. The transducer of claim 18 wherein the polymer comprises one of a silicone rubber and an acrylic.

23. The of claim 18 wherein the polymer has a thickness between about 1 micrometer and 2 millimeters.

24. The transducer of claim 18 wherein the polymer has an elastic modulus below about 100 MPa.

25. The transducer of claim 18 wherein the portion of the polymer deflects out of the plane of the polymer in response to he in electric field.

26. The transducer of claim 18 further comprising a stiff member attached to a portion of the polymer.

27. The transducer of claim 18 wherein the transducer is included in artificial muscle.