Electroactive polymers

• US 20040263028A1
• Filed: 07/16/2004
• Published: 12/30/2004
• 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., Pei, Qibing
• Granted Patent: US 7,049,732 B2
• Time in Patent Office: Days
• US Class Current: 310/307
• 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: H01G 5/16 using variation of distance between electrodes
• 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 30/098 Forming organic materials
• CPC Class Codes: H10N 30/2042 Cantilevers, i.e. having one fixed end
• CPC Class Codes: H10N 30/206 using only longitudinal or thickness displacement, e.g. d33 or d31 type devices
• CPC Class Codes: H10N 30/30 with mechanical input and electrical output, e.g. functioning as generators or sensors
• CPC Class Codes: H10N 30/308 Membrane type
• CPC Class Codes: H10N 30/857 Macromolecular compositions
• CPC Class Codes: H10N 30/87 Electrodes or interconnections, e.g. leads or terminals
• CPC Class Codes: H10N 30/878 the principal material being non-metallic, e.g. oxide or carbon based
• CPC Class Codes: Y10S 310/80 Piezoelectric polymers, e.g. PVDF
• CPC Class Codes: Y10T 29/49826 : Assembling or joining

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 transducer for converting between mechanical and electrical energy, the transducer comprising:

at least two electrodes; and

a polymer arranged in a manner which causes a portion of the polymer to deflect in response to a change in electric field and/or arranged in a manner which causes a change in electric field in response to deflection of the polymer,

wherein the polymer comprises one or more of a) a monoethylenically unsaturated monomer homopolymerizable to form a polymer having a glass transition temperature less than about 0 degrees Celsius, b) a thermoplastic elastomer, c) silicone and acrylic moieties and d) a layer laminated to at least a portion of one of the polymer and the at least two electrodes, and mechanically coupled to the polymer and/or one of the at least two electrodes.

2. The transducer of claim 1 wherein the monoethylenically unsaturated monomer is selected from a group consisting of isooctyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, dodecyl acrylate, hexyl acrylate, isononyl acrylate, isooctyl methacrylate, and 2-ethylhexyl methacrylate.

3. The transducer of claim 2 wherein the monomer contains a halogen.

4. The transducer of claim 3 wherein the halogen is fluorine.

5. The transducer of claim 1 wherein the transducer is included in one of an actuator, a generator, a sensor, a robot, a motor, a pump, and a toy.

6. The transducer of claim 1 wherein the thermoplastic elastomer is styrene-butadiene-styrene block copolymer.

7. The transducer of claim 1 wherein the polymer is a copolymer comprising silicone and acrylic moieties.

8. The transducer of claim 1 wherein the polymer is a polymer blend comprising a silicone elastomer and an acrylic elastomer.

9. The transducer of claim 1 wherein the layer is laminated to a portion of a first electrode and provides external mechanical protection to the first electrode.

10. The transducer of claim 9 wherein the transducer has an electromechanical efficiency greater than 80 percent.

11. The transducer of claim 1 wherein the layer distributes load across the polymer more uniformly during deflection.

12. The transducer of claim 1 wherein the layer has a higher stiffness than the polymer.

13. The transducer of claim 1 wherein the at least two electrodes comprises first and second electrodes and the layer is laminated between the first and second electrodes.

14. The transducer of claim 13 wherein the layer increases breakdown strength of the transducer.

15. The transducer of claim 1 wherein the layer is made from a compatible material relative to the polymer.

16. The transducer of claim 1 wherein the layer is used to compensate for manufacturing defects in the polymer.

17. The transducer of claim 1 wherein the layer provides greater polymer uniformity during deflection.

18. The transducer of claim 1 wherein the layer improves a mechanical property of the transducer.

19. The transducer of claim 1 wherein the layer is an adhesive layer.

20. The transducer of claim 1 wherein the polymer is rolled or folded.

21. The transducer of claim 20 wherein the polymer is folded and the electrodes are patterned.

22. The transducer of claim 20 wherein the at least two electrodes include a grounded outer exposed electrode.

23. The transducer of claim 1 wherein the polymer is elastically pre-strained.

24. The transducer of claim 1 wherein the polymer has an elastic modulus at most about 100 MPa.

25. The transducer of claim 1 wherein the polymer is elastically pre-strained by a factor in the range of about 1.5 times to 50 times an original area.

26. A method of fabricating a transducer comprising a polymer comprising an additive and one or more electrodes, the method comprising:

adding an additive to a polymer;

fixing a portion of the polymer to a solid member; and

forming the one or more electrodes on the polymer.

27. The method of claim 26 further comprising pre-straining a first portion of a polymer to form a pre-strained polymer.

28. The method of claim 26 wherein adding the additive to the polymer includes a centrifuge.

29. The method of claim 26 wherein the additive is added to the polymer in a solvent.

30. The method of claim 29 further comprising removing the solvent.

31. The method of claim 26 further comprising spin coating a polymer mixture to produce the polymer.

32. The method of claim 26 wherein the forming one or more electrodes comprises spraying the one or more electrodes onto the polymer using a mask.