ELECTROACTIVE POLYMER DEVICE AND METHOD FOR MANUFACTURING SUCH AN ELECTROACTIVE POLYMER DEVICE

Abstract

A method for manufacturing an electroactive polymer device which includes a layered structure including a dielectric polymer layer and an electrode layer, wherein the electrode layer is arranged on a surface of the dielectric polymer layer. The method includes: providing the dielectric polymer layer; determining a surface area location of a defect on a first surface of the dielectric polymer layer; creating an electrode layer including an area void of electrode layer material surrounding the surface area location, and the electrode layer includes a patch of electrode material covering the surface area location and a remainder part of the surface of the dielectric polymer layer surrounding the area void of electrode layer material, in which the patch and the remainder part are electrically isolated from one another.

Claims

1. Method for manufacturing an electroactive polymer device which comprises a layered structure comprising a dielectric polymer layer and an electrode layer, wherein the electrode layer is arranged on a surface of the dielectric polymer layer; the method comprising: providing the dielectric polymer layer; determining a surface area location of a defect on a first surface of the dielectric polymer layer; creating an electrode layer comprising an area void of electrode layer material surrounding the surface area location, wherein the electrode layer comprises a patch of electrode material covering the surface area location and a remainder part of the surface of the dielectric polymer layer surrounding the area void of electrode layer material, wherein the patch and the remainder part are electrically isolated from one another.

2. The method according to claim 1, wherein the step of creating an electrode layer comprises: forming a patterned area layer on a portion of the surface of the dielectric polymer layer surrounding the surface area location, while leaving the surface area location and a remainder of the surface of the dielectric polymer layer exposed; depositing an electrode layer material over at least the surface area location and the remainder of the surface of the dielectric polymer layer; removing the patterned area layer to create the electrode layer comprising an area void of the electrode layer material around the surface area location.

3. The method according to claim 2, further comprising curing the electrode layer after the removal of the patterned area layer.

4. The method according to claim 2, wherein the patterned area layer is selected from an adhesive sticker and a printed masking layer.

5. The method according to claim 1, wherein the step of creating the electrode layer comprises printing the electrode layer.

6. The method according to claim 5, further comprising curing the electrode layer after the step of printing.

7. The method according to claim 1, wherein the area void of electrode layer material has an annular shape, and is arranged centered around the surface area location.

8. The method according to claim 1, comprising a step of filling the area void of electrode layer material with a dielectric polymer material.

9. The method according to claim 1, wherein the defect is an electric breakdown defect, and the step of determining the surface area location of the electric breakdown defect comprises: providing a conductive substrate; arranging the dielectric polymer layer with a second surface opposite the first surface on the conductive substrate, such that the first surface is facing away from the conductive substrate; placing a movable electrode on or above the first surface; applying a high voltage between the movable electrode and the conductive substrate; moving the movable electrode over the first surface so as to expose the first surface of the dielectric polymer layer to the applied high voltage.

10. The method according to claim 9, wherein the electric breakdown defect is locally created in the dielectric polymer layer during the exposure of the first surface to the applied high voltage, and the method further comprises optically or electrically detecting a position of the created electric breakdown defect on the first surface and determining the surface area location from the position of the electric breakdown defect.

11. The method according to claim 1, wherein the layered structure of the dielectric polymer layer and the electrode layer is removed from the conductive substrate.

12. The method according to claim 1, wherein the creation of the electrode layer includes forming a conductive terminal in communication with the electrode layer on the dielectric polymer layer.

13. The method according to claim 11, further comprising forming a stack of a plurality of removed layered structures on each other, by adhering or gluing the dielectric polymer layer of one removed layered structure on the electrode layer of another removed layered structure that is adjacent in the stack.

14. An electroactive polymer device comprising a plurality of dielectric polymer layers and a plurality of electrode layers, the dielectric polymer layers and the electrode layers stacked on each other in alternating order, in which at least one electrode layer is an electrode layer comprising an area void of electrode layer material around a surface area location of a defect in an adjacent dielectric polymer layer, and the surface area location of the defect is covered by an electrically isolated patch of the electrode material.

15. An adhesive sticker suitable for use in the step of creating an electrode layer comprising an area void of electrode layer material in the method according to claim 1, the sticker comprising an annular shape with a central opening.

16. The method of claim 1, wherein the step of creating an electrode layer comprising an area void of electrode layer material further comprises placing an adhesive sticker on top of the dielectric polymer layer centering around the defect.

17. The adhesive sticker of claim 15, wherein the sticker further comprises a non-adhesive tab.

18. The method of claim 16, wherein the adhesive sticker further comprises a non-adhesive tab.

19. The method according to claim 3, wherein the patterned area layer is selected from an adhesive sticker and a printed masking layer.

20. The method according to claim 2, wherein the area void of electrode layer material has an annular shape, and is arranged centered around the surface area location.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0036] Embodiments will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts.

[0037] FIG. 1 shows a schematic view of an electrical proof-load testing facility as used in an embodiment;

[0038] FIG. 2 shows a top view of an adhesive sticker according to an aspect of the invention;

[0039] FIG. 3 shows a cross-section of a dielectric polymer layer with an adhesive sticker as manufactured by the method;

[0040] FIG. 4 shows the components of FIG. 3 with an electrode layer deposited;

[0041] FIG. 5 shows the components of FIG. 4 with the adhesive sticker removed;

[0042] FIG. 6 shows a cross-section of a layered structure as manufactured by the method, and

[0043] FIG. 7 shows a cross-section of an electroactive polymer device according to an aspect of the invention.

[0044] The figures are meant for illustrative purposes only, and do not serve as restriction of the scope or the protection as laid down by the claims.

DETAILED DESCRIPTION

[0045] Further advantages, features and details of the present invention will be explained in the following description of some embodiments thereof. In the description, reference is made to the attached figures.

[0046] FIG. 1 schematically shows a cross-section of a testing facility for locating any defects in a dielectric polymer (elastomer) layer 10 using an electric field. The testing facility comprises a conductive substrate 40, in this exemplary case a PET carrier web 41 with a conductive surface 42 which is formed by metallisation with a few nanometres of aluminium using physical vapour deposition. The conductive surface 42 is electrically grounded. The dielectric polymer layer 10 is arranged (e.g. coated) over the conductive surface 42. A conductive cylinder 43 which is connected to a high voltage power supply (not shown) is rolled over the dielectric polymer layer 10. In this way, a homogeneous electric field is applied across the dielectric polymer layer 10, in between the conductive surface 42 and the conductive cylinder 43. Wherever a weak point is present in the dielectric polymer layer 10, a dielectric breakdown causing a pinhole defect 30 across the thickness of the dielectric polymer layer 10 occurs. A weak point may be a small opening or thinned region in the dielectric polymer layer 10, caused by e.g. dirt, air bubbles or contamination. Pinholes caused by breakdowns are typically around 50 to 100 micrometre in diameter.

[0047] FIG. 2 schematically shows a top view of an adhesive sticker 50 according to an aspect of the invention. The adhesive sticker 50 is adapted to be placed around a pinhole as found by the method depicted in FIG. 1. To this end, the adhesive sticker 50 comprises an annular shape 51 surrounding a central opening 52, and a non-adhesive tab 53 for easy removal. The width w1 of the annular shape 51 (at either side of the central opening 51) is preferably at least 10 mm, while the width w2 of the central opening 51 itself is preferably at least 10 mm. The diameters are chosen such that they are sufficient to electrically isolate the pinhole defect from the surroundings. The rounded edges are preferred to avoid sharp transitions leading to electric field enhancement.

[0048] FIG. 3 schematically shows a cross-section of the dielectric polymer layer 10 of FIG. 1 on the conductive substrate 40. An adhesive sticker 50 as shown in FIG. 2 is placed on top of the dielectric polymer layer 10, centring around the pinhole defect 30. Determining the precise surface area location 33 of the pinhole defect 30 may be done for instance by high resolution cameras. Also information from the high voltage power supply and/or the moveable electrode 43, obtained during high voltage exposure of the dielectric polymer layer, may be used to determine the surface area location 33.

[0049] FIG. 4 schematically shows the components of FIG. 3, but now the dielectric polymer layer 10 and adhesive sticker 50 are coated with an electrode layer 20, which may be a conductive elastomer. The electrode layer 20 also covers the pinhole defect 30 entirely. Some electrode material may enter the pinhole defect 30.

[0050] FIG. 5 schematically shows that the adhesive sticker (shown in FIG. 2) is removed, e.g. using the non-adhesive tab 53, which results in the removal of a part of the electrode layer 20. The removal results in an annular area 32, which is now void of electrode layer 20, and electrically isolates a patch 31 of electrode material on top of the defect, from the remainder of the electrode layer 20. In this way, the pinhole defect 30 in the dielectric polymer layer 10 is electrically completely isolated from the remainder of the electrode layer 20.

[0051] FIG. 6 schematically shows the structure of FIG. 5, including the dielectric polymer layer 10 with pinhole defect 30 and the electrode layer 20, embedded in a stack of other layers forming a layered structure 1. The conductive substrate of FIGS. 1-5 is peeled away. The dielectric polymer layers 11, 12, 10, 13, 14 alternate with the electrode layers 21, 22, 20, 23, 24, while the electrode layers 21, 22, 20, 23, 24 are alternatingly offset to create contacts with different polarities. The pinhole defect 30 is now glued to the electrode layer 23 at one side and to the conductive patch 31 at the other side. The gluing at both sides prevents any tearing or crack propagation originating from the pinhole defect 30, which is particularly important when the layered structure 1 is stretched repeatedly.

[0052] FIG. 7 shows a cross-section of an electroactive polymer device 2 which includes the layered structure 1 of FIG. 2 as well as positive and negative polarity contacts 3, 4, constructed such that the electrode layers 21, 22, 20, 23, 24 are alternately of positive and negative polarity.

[0053] Notably, the pinhole defect 30 and the region of the dielectric polymer layer 10 surrounding the pinhole defect 30 are not exposed to an electric field, since the electrode material at both sides of the dielectric polymer layer 10 at the location of the pinhole defect 30 is of the same polarity. Therefore, premature dielectric failure at the location of the pinhole defect 30 is prevented.

[0054] The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. It will be apparent to the person skilled in the art that alternative and equivalent embodiments of the invention can be conceived and reduced to practice. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.