ELECTROACTIVE ACTUATORS, SYSTEMS EQUIPPED THEREWITH, AND METHODS OF USE AND MANUFACTURE

• US 20150091254A1
• Filed: 01/25/2013
• Published: 04/02/2015
• Est. Priority Date: 01/25/2012
• Status: Active Grant

• Current Assignee: Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University))
• Original Assignee: Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University))
• Inventors: Krutz, Gary William, Newell, Brittany Ann
• Granted Patent: US 9,683,663 B2
• Time in Patent Office: Days
• US Class Current: 277/312
• CPC Class Codes: F16J 15/008 with provision to put out of action at least one sealing; One sealing sealing only on standstill; Emergency or servicing sealings F16J15/164 takes precedence
• CPC Class Codes: F16J 15/022 characterised by structure or material
• CPC Class Codes: F16J 15/068 the packing swelling under working conditions
• CPC Class Codes: F16J 15/3284 characterised by their structure; Selection of materials
• 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 30/87 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

Abstract

Actuators and methods utilizing electrical properties of polymer materials. The actuators have a multilayer structure that includes an electroactive polymer layer between and bonded to first and second electrodes so that the polymer layer has a thickness dimension therebetween. The multilayer structure is adapted so that application of an electric potential to the electrodes causes the electroactive polymer layer to expand in at least one dimension thereof transverse to the thickness dimension of the electroactive polymer layer. The actuators can be used in sealing elements to provide a resealing capability once a condition has occurred of a type that may precede a seal failure.

Claims

1. An actuator having a multilayer structure comprising:

first and second electrodes formed of electrically-conductive polymer materials; and

an electroactive polymer layer formed of a dielectric elastomer, the electroactive polymer layer being between and bonded to the first and second electrodes so as to have a thickness dimension therebetween;

wherein the multilayer structure is adapted so that applying an electric potential to the first and second electrodes causes the electroactive polymer layer to expand in at least one dimension thereof transverse to the thickness dimension of the electroactive polymer layer.

2. The actuator according to claim 1, wherein the electroactive polymer layer is in a strain memory state induced by a pre-straining technique that expands the electroactive polymer layer and then releases the electroactive polymer layer to allow the electroactive polymer layer to substantially shrink to pre-strained dimensions thereof prior to bonding of the first and second electrodes thereto.

3. The actuator according to claim 1, wherein the electroactive polymer layer is in a strain memory state induced by a chemical pre-straining technique that swells the dielectric material and then allows the electroactive polymer layer to substantially shrink to pre-swelled dimensions thereof prior to bonding of the first and second electrodes thereto.

4. The actuator according to claim 1, wherein the dielectric elastomer is a copolymer comprising a fluoropolymer.

5. The actuator according to claim 1, wherein the actuator further comprises an elastomeric core completely surrounded by the multilayer structure.

6. The actuator according to claim 5, wherein the electroactive polymer layer is a first electroactive polymer layer of the actuator, and the actuator further comprises a second layer of an electroactive polymer material between and bonded to the elastomeric core and the first electrode.

7. The actuator according to claim 6, wherein the second layer of the electroactive polymer material is in a strain memory state induced by a pre-straining technique that expands the second layer and then releases the second layer to allow the second layer to substantially shrink to pre-strained dimensions thereof prior to bonding the elastomeric core and the first electrode thereto.

8. The actuator according to claim 6, wherein the second layer of the electroactive polymer material is in a strain memory state induced by a chemical pre-straining technique that swells the second layer and then allows the second layer to substantially shrink to pre-swelled dimensions thereof prior to bonding of the elastomeric core and the first electrode thereto.

9. The actuator according to claim 1, the actuator further comprising means for monitoring distortion of the actuator, the actuator being connected to means for applying the electric potential in response to the monitoring means.

10. The actuator according to claim 9, wherein the monitoring means comprises:

an electrically-conductive polymer sensing element integrally incorporated into the actuator;

means for applying a second electric potential to the polymer sensing element;

means for sensing an electric signal generated by the polymer sensing element in response to the polymer sensing element physically responding to distortion of the actuator; and

means for applying the electric potential to the first and second electrodes if the electric signal exceeds a predetermined threshold value corresponding to the distortion of the actuator attaining a predetermined level.

11. The actuator according to claim 1, wherein the actuator is a sealing element.

12. The actuator according to claim 11, wherein the sealing element has an annular shape and the multilayer structure completely surrounds an elastomeric core.

13. The system according to claim 12, wherein the sealing element is disposed in a groove, distortion of the sealing element causes the sealing element to occupy a reduced cross-sectional area of the groove, and applying the electric potential to the first and second electrodes causes the sealing element to expand to occupy an increased cross-sectional area of the groove.

14. A system for attaining a sealing effect at a sealing interface, the system having a sealing element comprising:

an elastomeric core; and

a multilayer structure on the elastomeric core, the multilayer structure comprising first and second electrodes and an electroactive polymer material therebetween and bonded thereto, the multilayer structure being adapted so that applying an electric potential to the first and second electrodes causes the electroactive polymer material to expand in at least one dimension thereof to increase the sealing effect of the sealing element at the sealing interface.

15. The system according to claim 14, wherein the electroactive polymer material is a dielectric elastomer.

16. The system according to claim 14, wherein the electroactive polymer material is in a strain memory state induced by a pre-straining technique that expands the electroactive polymer material and then releases the electroactive polymer material to allow the electroactive polymer material to substantially shrink to pre-strained dimensions thereof prior to bonding of the first and second electrodes thereto.

17. The system according to claim 14, wherein the electroactive polymer material is in a strain memory state induced by a chemical pre-straining technique that swells the electroactive polymer material and then allows the electroactive polymer material to substantially shrink to pre-swelled dimensions thereof prior to bonding of the first and second electrodes thereto.

18. The system according to claim 15, wherein the dielectric elastomer is a copolymer comprising a fluoropolymer.

19. The system according to claim 14, wherein the first and second electrodes and the electroactive polymer material each define a layer of the multilayer structure, and the sealing element further comprises an elastomeric core completely surrounded by the multilayer structure.

20. The system according to claim 19, wherein the layer of the electroactive polymer material is a first electroactive polymer layer of the multilayer structure, and the multilayer structure further comprises a second layer of the electroactive polymer material between the elastomeric core and the first electroactive polymer layer.

21. The system according to claim 14, wherein the first and second electrodes are formed of an electrically-conductive polymer material.

22. The system according to claim 14, the system further comprising means for monitoring distortion of the sealing element and means for applying the electric potential in response to the monitoring means.

23. The system according to claim 22, wherein the monitoring means comprises:

an electrically-conductive polymer sensing element integrally incorporated into the sealing element;

means for applying a second electric potential to the polymer sensing element;

means for sensing an electric signal generated by the polymer sensing element in response to the polymer sensing element physically responding to the distortion of the sealing element; and

means for applying the electric potential to the first and second electrodes if the electric signal exceeds a predetermined threshold value corresponding to the distortion of the sealing element attaining the predetermined level.

24. The system according to claim 14, wherein the sealing element is an O-ring, a face seal, or a gasket.

25. The system according to claim 14, wherein the sealing element has an annular shape and the multilayer structure completely surrounds the elastomeric core.

26. The system according to claim 25, wherein the sealing element is disposed in a groove, the distortion of the sealing element causes the sealing element to occupy a reduced cross-sectional area of the groove, and applying the electric potential to the first and second electrodes causes the sealing element to expand to occupy an increased cross-sectional area of the groove.

27. A method of maintaining a sealing interface, the method comprising:

placing a sealing element at the sealing interface to attain a sealing effect at the sealing interface, the sealing element comprising first and second electrodes and an electroactive polymer material therebetween and bonded thereto;

monitoring distortion of the sealing element; and

in the event that the distortion of the sealing element attains a predetermined level, applying an electric potential to the first and second electrodes to cause the electroactive polymer material to expand in at least one dimension thereof to increase the sealing effect of the sealing element at the sealing interface.

28. The method according to claim 27, wherein the electroactive polymer material is a dielectric elastomer.

29. The method according to claim 28, wherein the dielectric elastomer is a copolymer comprising a fluoropolymer.

30. The method according to claim 27, the method further comprising inducing a strain memory state in the electroactive polymer material by a pre-straining technique that expands the electroactive polymer material and then releases the electroactive polymer material to allow the electroactive polymer material to substantially shrink to pre-strained dimensions thereof prior to bonding of the first and second electrodes thereto.

31. The method according to claim 27, the method further comprising inducing a strain memory state in the electroactive polymer material by a chemical pre-straining technique that swells the electroactive polymer material and then allows the electroactive polymer material to substantially shrink to pre-swelled dimensions thereof prior to bonding of the first and second electrodes thereto.

32. The method according to claim 27, wherein the first and second electrodes and the electroactive polymer material each define a layer, the first and second electrodes and the electroactive polymer material together define a multilayer structure, and the sealing element further comprises an elastomeric core completely surrounded by the multilayer structure.

33. The method according to claim 32, wherein the layer of the electroactive polymer material is a first electroactive polymer layer of the multilayer structure, and the multilayer structure further comprises a second layer of the electroactive polymer material between the elastomeric core and the first electroactive polymer layer.

34. The method according to claim 33, wherein the second layer of the electroactive polymer material is in a strain memory state induced by a pre-straining technique that expands the second layer and then releases the second layer to allow the second layer to substantially shrink to pre-strained dimensions thereof prior to bonding the elastomeric core and the first electrode thereto.

35. The method according to claim 27, wherein the first and second electrodes are formed of a flexible electrically-conductive polymer material.

36. The method according to claim 27, wherein the monitoring of the distortion of the sealing element is performed with an electrically-conductive polymer sensing element integrally incorporated into the sealing element, and the monitoring comprises:

applying a second electric potential to the polymer sensing element;

sensing an electric signal generated by the polymer sensing element in response to the polymer sensing element physically responding to the distortion of the sealing element; and

then

applying the electric potential to the first and second electrodes if the electric signal exceeds a predetermined threshold value corresponding to the distortion of the sealing element attaining the predetermined level.

37. The method according to claim 27, wherein the sealing element is an O-ring, a face seal, or a gasket.

38. The method according to claim 27, wherein the sealing element has an annular shape.

39. The method according to claim 38, wherein the sealing element is disposed in a groove, the distortion of the sealing element causes the sealing element to occupy a reduced cross-sectional area of the groove, and the applying of the electric potential to the first and second electrodes causes the sealing element to expand to occupy an increased cross-sectional area of the groove.

40. A method of fabricating an actuator, the method comprising:

inducing a strain memory state in an electroactive polymer material by a pre-straining technique that expands the electroactive polymer material and then releases the electroactive polymer material to allow the electroactive polymer material to substantially shrink to pre-strained dimensions thereof; and

then

bonding first and second electrodes to opposite surfaces of the electroactive polymer material.

41. The method according to claim 40, wherein the electroactive polymer material is a fluoropolymer.

42. The method according to claim 40, wherein the electroactive polymer material is an FKM material.

43. The method according to any one of claims 40, 41 and 42, wherein the pre-straining technique is a chemical pre-straining technique comprising:

contacting the electroactive polymer layer with a chemical that causes the electroactive polymer layer to swell; and

then

removing the electroactive polymer layer from contact with the chemical to allow the electroactive polymer layer to substantially shrink to pre-swelled dimensions thereof prior to bonding of the first and second electrodes thereto.

44. The method according to claim 43, wherein the electroactive polymer material is a fluoropolymer.

45. The method according to claim 43, wherein the electroactive polymer material is an FKM material.