Multilayer composite and a method of making such

• US 20070114885A1
• Filed: 11/03/2006
• Published: 05/24/2007
• Est. Priority Date: 11/02/2000
• Status: Active Grant

• Current Assignee: Danfoss A/S
• Original Assignee: Danfoss A/S
• Inventors: Gravesen, Peter, Benslimane, Mohamed
• Granted Patent: US 7,548,015 B2
• Time in Patent Office: Days
• US Class Current: 310/311
• CPC Class Codes: B81B 2201/038 Microengines and actuators not provided for in B81B2201/031 - B81B2201/037
• CPC Class Codes: B81B 3/007 For controlling stiffness, e.g. ribs
• CPC Class Codes: F04B 43/043 Micropumps
• CPC Class Codes: F04B 43/14 having plate-like flexible members
• CPC Class Codes: H02N 1/002 Electrostatic motors
• CPC Class Codes: H02N 1/006 of the gap-closing type H02N1/004 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 30/05 Manufacture of multilayered piezoelectric or electrostrictive devices, or parts thereof, e.g. by stacking piezoelectric bodies and electrodes
• CPC Class Codes: H10N 30/067 Forming single-layered electrodes of multilayered piezoelectric or electrostrictive parts
• CPC Class Codes: H10N 30/098 Forming organic materials
• CPC Class Codes: H10N 30/206 using only longitudinal or thickness displacement, e.g. d33 or d31 type devices
• CPC Class Codes: H10N 30/50 having a stacked or multilayer structure
• CPC Class Codes: H10N 30/506 having a cylindrical shape and having stacking in the radial direction, e.g. coaxial or spiral type rolls
• CPC Class Codes: H10N 30/871 Single-layered electrodes of multilayer piezoelectric or electrostrictive devices, e.g. internal electrodes
• CPC Class Codes: Y10T 428/24521 with component conforming to contour of nonplanar surface

Abstract

A multilayer composite includes at least two composites, each composite having a film and an electronically conductive layer. Several composites are laminated to provide an increased conversion between mechanical and electrical energies not only due to the multiplication of the effect of each layer, but also due to the fact that the multilayer structure itself renders the multilayer composite more rigid. In addition, the multilayer structure facilitates application of an electrical field over thinner portions of the structure, thereby requiring much less potential difference between electrodes.

Claims

1. A multilayer composite comprising at least two composites, each composite comprising:

a film made of a dielectric material and having a front surface and rear surface, the front surface comprising a surface pattern of raised and depressed surface portions, and

a first electrically conductive layer being deposited onto the surface pattern, the electrically conductive layer having a corrugated shape which is formed by the surface pattern of the film.

2. The multilayer composite according to claim 1, wherein the dielectric material is a polymer.

3. The multilayer composite according to claim 1, wherein the composites are arranged with the rear surfaces towards each other.

4. The multilayer composite according to claim 3 comprising a composite arranged with its front surface facing a front surface of one of the at least two composites.

5. The multilayer composite according to claim 1, wherein the composites are arranged so that the rear surface of one composite is facing the front surface of an adjacent composite.

6. The multilayer composite according to claim 1, wherein the multilayer composite is made from a number of composites sufficient to achieve an area moment of a cross section for bending of the multilayer composite which is at least 2 times an average of an area moment of inertia of each composite individually.

7. The multilayer composite according to claim 1, wherein the composites are adhesively bonded to each other.

8. The multilayer composite according to claim 7, wherein the composites are adhesively bonded by the use of an adhesive having hardness at most in the order of magnitude of that of each composite individually.

9. The multilayer composite according to claim 1, wherein the surface pattern of the film of each composite is substantially identical.

10. The multilayer composite according to claim 1, wherein the surface pattern of the film of each composite comprises waves forming crests and troughs extending in one common direction, the waves defining a compliance of the electrically conductive layers to deform in a direction perpendicular to the common direction and thereby an anisotropic characteristics of the multilayer composite.

11. The multilayer composite according to claim 10, wherein the waves have a shape which is periodically repeated.

12. The multilayer composite according to claim 10, wherein each wave defines a height being a shortest distance between a crest and neighbouring troughs, a largest wave having a height of at most 110 percent of an average wave height.

13. The multilayer composite according to claim 10, wherein each wave defines a height being a shortest distance between a crest and neighbouring troughs, a smallest wave having a height of at least 90 percent of an average wave height.

14. The multilayer composite according to claim 10, wherein the film has an average thickness being between 10 and 200 μ

m.

15. The composite according to claim 10, wherein a ratio between an average height of the waves and an average thickness of the film is between 1/50 and 1/2.

16. The composite according to claim 10, wherein an average height of the waves is between 1/3 and 20 μ

m.

17. The composite according to claim 10, wherein the waves have a wavelength defined as the shortest distance between two crests, and wherein a ratio between an average height of the waves and an average wavelength is between 1/30 and 2.

18. The composite according to claim 10, wherein a ratio between an average thickness of the first electrically conductive layer and an average height of the waves is between 1/1000 and 1/50.

19. The composite according to claim 10, wherein the first electrically conductive layer has a thickness in the range of 0.01-0.1 μ

m.

20. The multilayer composite according to claim 1, comprising composites being substantially (in the description, this will be described as at least 10 times) longer in a lengthwise direction than in a perpendicular crosswise direction.

21. The multilayer composite according to claim 20, wherein the surface pattern forms wave crests and troughs extending essentially in the lengthwise direction.

22. The multilayer composite according to claim 21, wherein the surface pattern forms wave crests and troughs extending essentially in the crosswise direction.

23. The multilayer composite according to claim 1, wherein the surface pattern comprises a plurality of identical sub patterns.

24. The multilayer composite according to claim 1, wherein the composites are arranged relative to each other to provide a shortest possible distance between crests of one layer and crests of another layer.

25. The multilayer composite according to claim 10, wherein the composites are arranged relative to each other to provide a longest possible distance between crests of one layer and crests of another layer.

26. The multilayer composite according to claim 10, wherein the multilayer composite is pre-strained in a direction perpendicular to the direction of the crests and troughs.

27. The multilayer composite according to claim 26, wherein the multilayer composite is stretched by an elastically deformable structure.

28. The multilayer composite according to claim 1, wherein the multilayer composite is arranged in connection with electrical control means to convert between electrical and mechanical energies.

29. The multilayer composite according to claim 28, wherein the multilayer composite is arranged relative to an object to exert a pressure on the object by use of electrostatic forces.

30. The multilayer composite according to claim 1, wherein the multilayer composite comprises a peripheral edge which is covered with an electrically isolating layer.

31. The multilayer composite according to claim 1, wherein the film is made of silicone elastomers, acrylic elastomers, or combinations thereof.

32. The multilayer composite according to claim 1, wherein the films of the composites are adhesive to bond directly onto an adjacent composite.

33. The multilayer composite according to claim 1, wherein the first electrically conductive layer is a metal.

34. The multilayer composite according to claim 33, wherein the metal is selected from a group consisting of silver, gold, and nickel.

35. The multilayer composite according to claim 1, wherein the two composites form part of one single continuous film made of a dielectric material having on a front surface a surface pattern of raised and depressed surface portions, a first electrically conductive layer being deposited onto a first portion of the surface pattern, a second electrically conductive layer being deposited onto a second portion of the surface pattern, and the first and second electrically conductive layers being electrically isolated from each other, wherein the film is folded, rolled or otherwise formed into a multilayer structure in which the first and second electrically conductive layers are located alternately between layers of the film.

36. The multilayer composite according to claim 1, wherein the films of the composites form dielectric layers having first and second surfaces towards the electrically conductive layers, the electrically conductive layers defining:

an active portion of the actuator wherein electrode portions of the electrically conductive layers cover both surfaces of the dielectric layers;

a first passive portion and a second passive portion in which portions only one surface of the dielectric layers is covered by one of the conductive layers;

wherein the first passive portion is defined by a contact portion of the electrically conductive layer on the first surface, and the second passive portion is defined by a contact portion of the electrically conductive layer on the second surface.

37. The multilayer composite according to claim 36, further comprising an electrical connector attached to each contact portion, the electrical connector extending beyond an edge portion of the multilayer composite to facilitate connection of the electrically conductive layer to a power supply.

38. The multilayer composite according to claim 1, wherein each composite has a shape which is essentially unaffected by contact between the film and the electrically conductive layer.

39. The multilayer composite according to claim 1, wherein the resistivity of the dielectric material is larger than 10¹⁰ Ω

·

cm.

40. The multilayer composite according to claim 1, wherein the resistivity of the electrically conductive material is less than 10⁻

4 Ω

·

cm.

41. The multilayer composite according to claim 1, wherein the resistivity of the dielectric material is larger than 10¹⁰ Ω

·

cm per composite.

42. The multilayer composite according to claim 1, wherein the resistivity of the electrically conductive material is less than 10⁻

4 Ω

·

cm per composite.

43. A transducer comprising a multilayer composite according to claim 1.

44. A multilayer composite comprising at least two layers of composite, each composite layer comprising:

a film made of a dielectric material and having a front surface and rear surface, the front surface comprising a surface pattern of raised and depressed surface portions, and

a first electrically conductive layer being deposited onto the surface pattern, the electrically conductive layer having a corrugated shape which is formed by the surface pattern of the film.

45. The multilayer composite according to claim 44, wherein the composite layers are arranged with the rear surfaces towards each other.

46. The multilayer composite according to claim 44, wherein the composite layers are adhesively bonded to each other.

47. The multilayer composite according to claim 44, wherein the film of each composite layer comprises waves forming crests and troughs extending in one common direction.

48. The multilayer composite according to claim 47, wherein composite layers are arranged relative to each other to provide a shortest possible distance between crests of one layer and crests of another layer.

49. The multilayer composite according to claim 47, wherein the composite layers are arranged relative to each other to provide a longest possible distance between crests of one layer and crests of another layer.