PIEZOELECTRIC MACRO-FIBER COMPOSITE ACTUATOR AND METHOD FOR MAKING SAME

• US 20030056351A1
• Filed: 10/29/1999
• Published: 03/27/2003
• Est. Priority Date: 10/29/1999
• Status: Active Grant

• Current Assignee: National Aeronautics and Space Administration (Government of the United States of America)
• Original Assignee: National Aeronautics and Space Administration (Government of the United States of America)
• Inventors: BRYANT, ROBERT G., HIGH, JAMES W., HELLBAUM, RICHARD F., FOX, ROBERT L., LITTLE, BRUCE D., MIRICK, PAUL H., WILKIE, W. KEATS, JALINK, ANTONY Jr.
• Granted Patent: US 6,629,341 B2
• Time in Patent Office: Days
• US Class Current: 29/25.35
• CPC Class Codes: H04R 17/005 using a piezoelectric polymer
• CPC Class Codes: H10N 30/06 Forming electrodes or interconnections, e.g. leads or terminals
• CPC Class Codes: H10N 30/092 Forming composite materials
• CPC Class Codes: H10N 30/206 using only longitudinal or thickness displacement, e.g. d33 or d31 type devices
• CPC Class Codes: H10N 30/208 using shear or torsion displacement, e.g. d15 type devices
• CPC Class Codes: H10N 30/702 based on piezoelectric or electrostrictive fibres
• CPC Class Codes: H10N 30/87 Electrodes or interconnections, e.g. leads or terminals
• CPC Class Codes: Y10T 156/1044 of parallel stacked sheets only
• CPC Class Codes: Y10T 156/1092 All laminae planar and face to face
• CPC Class Codes: Y10T 156/1093 with covering of discrete laminae with additional lamina
• CPC Class Codes: Y10T 156/1095 Opposed laminae are running length webs
• CPC Class Codes: Y10T 29/42 Piezoelectric device making
• CPC Class Codes: Y10T 29/435 Solid dielectric type
• CPC Class Codes: Y10T 29/49005 Acoustic transducer
• CPC Class Codes: Y10T 29/49007 Indicating transducer
• CPC Class Codes: Y10T 29/4908 Acoustic transducer
• CPC Class Codes: Y10T 29/49083 Heater type
• CPC Class Codes: Y10T 29/49126 Assembling bases
• CPC Class Codes: Y10T 29/49128 Assembling formed circuit to base

Abstract

A method for fabricating a piezoelectric macro-fiber composite actuator comprises providing a piezo-electric material which has a first side and a second side. The method further comprises cutting the piezoelectric material to provide a plurality of piezoelectric fibers in juxtaposition. Two electrically conductive films are then adhesively bonded to the two sides of the piezo-electric material. The first film has first and second conductive patterns formed thereon which are electrically isolated from one another and in electrical contact with the piezo-electric material. In one embodiment, the second film does not have any conductive patterns. The first and second conductive patterns of the first film each have a plurality of electrodes to form a pattern of interdigitated electrodes. In another embodiment, the second film has a pair of conductive patterns similar to the conductive patterns of the first film. In another embodiment, the piezoelectric macro-fiber composite actuator further comprises a pair of anisotropically conductive sheets each positioned between one of the electrically conductive films and one side of the piezoelectric material.

Claims

1. A method of fabricating a piezoelectric macro-fiber composite actuator, comprising the steps of:

providing a structure comprising a piezo-electric material having a first side and a second side;

providing a first film having a first and second conductive pattern formed thereon, the first conductive pattern being electrically isolated from the second conductive pattern, the first and second conductive patterns each having a plurality of electrodes that cooperate to form a pattern of interdigitated electrodes;

providing a second film; and

bonding the first and second films to the first and second sides, respectively, of the structure such that the conductive patterns of the first film electrically contact the piezo-electric material structure.

2. The method according to claim 1 wherein the structure of piezo-electric material comprises a monolithic piezoelectric wafer.

3. The method according to claim 1 wherein the second film has a first conductive pattern and a second conductive pattern, the first conductive pattern of the second film being electrically isolated from the second conductive pattern of the second film, the first and second conductive patterns of the second film each having a plurality of electrodes that cooperate to form a pattern of interdigitated electrodes, the bonding step further comprising the step of positioning the first and second films so that the conductive patterns of the first and second films are substantially aligned.

4. The method according to claim 3 further comprising a pair of electrically conductive extensions, each extension being attached to a corresponding conductive pattern.

5. The method according to claim 1 wherein the piezo-electric material structure comprises a plurality of fibers in juxtaposition, each fiber having a first side and a second side, the first and second sides of the fibers defining the first and second sides, respectively, of the piezo-electric material structure.

6. The method according to claim 5 wherein each fiber has a substantially rectangular cross-section.

7. The method according to claim 5 wherein each pair of adjacent fibers are separated by a channel.

8. The method according to claim 1 further comprising the step of slicing the structure to provide a plurality of piezoelectric fibers in juxtaposition before bonding the first and second films to the first and second sides of the structure.

9. A method according to claim 1 further comprising the steps of:

providing a backing sheet having an adhesive side;

positioning the structure on the backing sheet such that the first side of the plurality of fibers are adhesively attached to the adhesive side of the backing sheet; and

slicing the piezo-electric material structure while positioned on the backing sheet to provide a plurality of piezoelectric fibers in juxtaposition.

10. The method according to claim 9 wherein the backing sheet is fabricated from a polymer.

11. The method according claim 9 wherein the bonding step further comprises:

first bonding the second film to the second side of the plurality of fibers;

removing the adhesive backing from the first side of the plurality of fibers; and

bonding the first film to the first side of the plurality of fibers.

12. The method according to claim 9 wherein the conductive patterns are made of copper.

13. The method according to claim 8 wherein the step of slicing produces a plurality of fibers which extend in the direction of the longitudinal axes of the first and second films.

14. The method according to claim 8 wherein the step of slicing provides channels intermediate each pair of adjacent fibers, the method further comprising the step of applying an epoxy to the fibers to fill in the channels and eliminate air pockets.

15. The method according to claim 1 wherein the first and second films each have first and second sides, the bonding step comprising:

applying a first adhesive layer to the first side of the first film;

placing the first side of the first film on the first side of the piezo-electric material structure;

curing the first adhesive layer;

applying the second adhesive layer to the first side of the second film;

placing the first side of the second film on the second side of the piezo-electric material structure; and

curing the second adhesive layer.

16. The method according to claim 3 wherein the piezo-electric material structure comprises a wafer of piezo-electric material, the method further comprising the steps of:

slicing the wafer to provide a plurality of fibers separated by channels, each fiber having a first side and a second side, the first and second sides of the fibers defining the first and second sides, respectively, of the piezo-electric material structure; and

bonding the first and second films to the first and second sides, respectively, of the fibers so that the conductive patterns electrically contact the piezo-electric material.

17. The method according to claim 16 wherein each film has a longitudinally extending axis and each fiber extends in the direction of the longitudinally extending axes of the films.

18. The method according to claim 17 wherein each electrode is generally perpendicular to the longitudinally extending portion from which it extends, the electrodes of the first and second conductive patterns being substantially perpendicular to the fibers.

19. The method according to claim 16 wherein the electrodes within each film are angulated with respect to the longitudinally extending portion of the film.

20. The method according to claim 19 wherein the degree of angulation of the electrodes with respect to the longitudinally extending portion is about 45°

.

21. The method according to claim 19 wherein each fiber is sliced at an angle with respect to the longitudinally extending edge of the films.

22. The method according to claim 21 wherein each electrode extends in a direction substantially perpendicular to the fibers.

23. The method according to claim 1 further comprising the step of attaching electrically conductive extensions to the first and second conductive patterns.

24. The method according to claim 1 further comprising the steps of:

providing a pair of anisotropically conductive sheets;

bonding each anisotropically conductive sheet to a respective side of the structure; and

bonding the first film to one anisotropically conductive sheet such that the first and second conductive patterns contact the anisotropically conductive sheet, and bonding the second film to the other anisotropically conductive sheet.

25. The method according to claim 1 wherein the step of providing the structure comprising a piezo-electric material comprises the step of:

providing a plurality of wafers of piezo-electric material;

bonding the wafers together to form a stack; and

slicing the stack in the direction of the thickness of the stack to provide at least one sheet of piezo-electric material having a first side and a second side that defines the first side and second side, respectively, of the piezo-electric material structure.

26. An apparatus comprising:

a piezo-electric material having a first side and a second side;

a first film bonded to the first side of the material, the first film having a first side and a second side, the film further comprising first and second conductive patterns, each conductive pattern being in electrical contact with the piezo-electric material, the first conductive pattern being electrically isolated from the second conductive pattern, the first and second conductive patterns each having a plurality of electrodes which form a pattern of interdigitated electrodes; and

a second film bonded to the second side of the material.

27. The apparatus of claim 26 wherein the piezo-electric material comprises a monolithic piezoelectric wafer.

29. The apparatus of claim 26 wherein the first and second films are fabricated from a polyimide film.

30. The apparatus of claim 26 wherein the piezo-electric material structure comprises a plurality of fibers in juxtaposition, each fiber having a first side and a second side, the first and second sides of the fibers defining the first and second sides, respectively, of the piezo-electric material.

31. The apparatus of claim 30 wherein each fiber has a substantially rectangular cross-section.

32. The apparatus of claim 30 wherein the first film and the second film each have a longitudinally extending axis and wherein each fiber has a longitudinally extending axis, the longitudinally extending axis of each fiber being substantially parallel to the longitudinally extending axes of the films.

33. The apparatus of claim 30 wherein each pair of adjacent fibers are separated by a channel, the apparatus further comprising a layer of epoxy disposed over the fibers and in the channels.

34. The apparatus of claim 30 wherein the first film and the second film each have a longitudinally extending axis and wherein each fiber has a longitudinally extending axis, the longitudinally extending axis of each fiber being angulated with respect to the longitudinally extending axes of the films and wherein the electrodes of each film are angulated with respect to the longitudinally extending axes of the films.

35. The apparatus of claim 34 wherein the degree of angulation of the electrodes with respect to the longitudinally extending axes of the films is about 45°

.

36. The apparatus of claim 34 wherein the interdigitated electrodes extend in a direction substantially perpendicular to the axes of the fibers.

37. The apparatus of claim 26 further comprising:

a first anisotropically conductive sheet disposed between and bonded to the first film and the first side of the piezo-electric material; and

a second anisotropically conductive sheet disposed between and bonded to the second film and the second side of the piezo-electric material.

28. The apparatus of claim 28 wherein the second film has a first conductive pattern and a second conductive pattern, each conductive pattern being in electrical contact with the piezo-electric material, the first conductive pattern of the second film being electrically isolated from the second conductive pattern of the second film, the first and second conductive patterns of the second film each having a plurality of electrodes which form a pattern of interdigitated electrodes.

38. A piezoelectric macro-fiber composite actuator, comprising:

a plurality of piezoelectric fibers in juxtaposition, each fiber having a first side and a second side, each pair of adjacent fibers being separated by a channel;

a first adhesive layer disposed over the first sides of the fibers and within the channels;

a first film bonded to the first sides of the fibers, the first film comprising at least one conductive pattern, each conductive pattern being electrically isolated from any other conductive pattern and in electrical contact with the piezo-electric fibers, said at least one conductive pattern having a plurality of electrodes to form a pattern of interdigitated electrodes;

a second adhesive layer disposed over the second sides of the fibers and within the channel; and

a second film bonded to the second sides of the fibers, the second film comprising at least one conductive pattern, said at least one conductive pattern being electrically isolated from any other conductive pattern and in electrical contact with the piezo-electric fibers, said at least one conductive pattern having a plurality of electrodes to form a pattern of interdigitated electrodes, said at least one conductive pattern of the first film being substantially aligned with said at least one conductive pattern of the second film.