Electroactive polymer device and method for manufacturing such an electroactive polymer device

Abstract

A method for manufacturing an electroactive polymer device, the electroactive polymer device comprising a layered structure, the layered structure comprising a dielectric polymer layer and an electrode layer, wherein the electrode layer is disposed on a surface of the dielectric polymer layer. The method comprises: providing a dielectric polymer layer; determining a surface area location of a defect on a first surface of the dielectric polymer layer; producing an electrode layer comprising an area free of electrode layer material surrounding the surface area location, and the electrode layer comprising a patch of electrode material covering the surface area location and a remainder of the surface of the dielectric polymer layer surrounding the area free of electrode layer material, wherein the patch and the remainder are electrically isolated from each other.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an electroactive polymer device. The present invention also relates to an electroactive polymer device and an adhesive paste used in the method. Background Art

[0002] Energy conversion systems that convert mechanical energy into electrical energy are commonly used today. One example of such a system is the dielectric electroactive polymer (DEAP) based device disclosed in WO2010 / 146457.

[0003] Such a DEAP-based device or DEAP device comprises a dielectric elastomer carrier layer. An electrode layer is arranged on the surface of the dielectric elastomer layer. The DEAP device can be considered as a variable capacitor, whose capacitance varies as a function of the amount of deformation applied to the DEAP material layer. Due to the external force, the electroactive polymer material can be stretched, i.e. elastically deformed, which causes the distance between the electrode layers to decrease. When the external force decreases and the electroactive polymer layer relaxes, the distance increases again. Energy can be obtained from the DEAP device by applying a charge on the capacitor with essentially maximum deformation and removing the charge with minimum deformation. Alternatively, by adjusting the charge on the capacitor, the mechanical properties of the capacitor can be controlled.

[0004] Increasing the electric field in a DEAP device is very important because it has a quadratic contribution to the amount of electrical energy that can be harvested. The harvested energy density per amount of material will ultimately drive commercial applications.

[0005] The maximum electric field that can be applied to a DEAP device in operation is generally controlled by the intrinsic properties of the material (dielectric breakdown strength), control and cleanliness of the manufacturing process (bubbles or particles will significantly reduce the dielectric breakdown strength), the volume of material exposed to the electric field, electrical aging, and electric field enhancement at specific locations.

[0006] All of these parameters affect the maximum electric field of a DEAP device. In general, it would be desirable to provide a method for fabricating a DEAP device that allows for increasing the electric field and / or improving fabrication efficiency and / or provides an alternative to conventional methods. Summary of the invention

[0007] According to one aspect of the present invention, a method for manufacturing an electroactive polymer device is provided, the electroactive polymer device comprising a layered structure, the layered structure comprising a dielectric polymer layer and an electrode layer, wherein the electrode layer is arranged on the surface of the dielectric polymer layer; the method comprises: providing the dielectric polymer layer; determining a surface area position of a defect on a first surface of the dielectric polymer layer; generating an electrode layer comprising an area surrounding the surface area position that does not contain electrode layer material; wherein the electrode layer comprises a patch of electrode material covering the surface area position and a remaining portion of the surface of the dielectric polymer layer surrounding the area that does not contain electrode layer material, wherein the patch and the remaining portion are electrically isolated from each other.

[0008] The present method allows to remove all weak points in the dielectric polymer layer from exposure to the electric field. In this way, electrical failure of the DEAP device during use is prevented. The method also ensures stable mechanical properties in the event of repeated stretching, which is a significant feature of such DEAP devices. In other words, tearing of the dielectric polymer layer is prevented. More importantly, the process reduces the volume dependence of the dielectric failure probability. The removal of volume dependence is a major improvement in large DEAP generators containing thousands of square meters of DEAP film. The method allows much higher operating electric fields and therefore significantly increases energy generation. When the present method is applied, a three-fold increase in energy output can be expected in a typical DEAP device.

[0009] When a large volume of material is required, the operating electric field is significantly reduced. The reduction in the field is attributed to the higher probability of defects in the bulk material. The reduction in the electric field is essentially related to the purity of the film. By ensuring that the location of the defects will not be affected by the electric field, the electric field can therefore be increased and the failure probability is no longer dependent on the volume.

[0010] The construction of the patch on top of the surface area location repairs the pinholes or defects at both sides of the dielectric polymer layer and ensures stable mechanical properties, i.e., so that the pinholes do not propagate into cracks. Thus, the structure combines the functions of electrical isolation and the repair of defects. The patch is preferably circular. The area without electrode layer material preferably has a ring shape.

[0011] Preferably, the dielectric polymer layer is an elastomeric layer, wherein the elastomer may be a polymer selected from silicone polymers, polyurethanes, urethane polymers and acrylic polymers.

[0012] The dielectric polymer layer preferably has a thickness of 10 to 100 microns, while the electrode layer preferably has a thickness of about a few nanometers to less than 100 microns. In one embodiment, the layered structure consists of a dielectric polymer layer and at least one electrode layer.

[0013] The area without electrode layer may be covered or filled with a dielectric polymer so that it electrically isolates the patch of electrode layer material from the rest.

[0014] In one embodiment, the step of producing an electrode layer includes: forming a patterned area layer on a portion of the surface of the dielectric polymer layer surrounding the surface area location, while exposing the surface area location and the remaining portion of the surface of the dielectric polymer layer; depositing electrode layer material on at least the surface area location and the remaining portion of the surface of the dielectric polymer layer; removing the patterned area layer to produce an electrode layer including an area surrounding the surface area location that does not contain electrode layer material.

[0015] An advantage of this embodiment is that the areas free of electrode layer material are consistent and reliable, and the likelihood of accidental electrode material deposition in the electrode-free areas is negligible.

[0016] In one embodiment, the method further comprises curing the electrode layer after removing the patterned region layer. The curing step after removing the patterned region layer increases the durability of the electrode layer while ensuring that the patterned region layer can be easily removed.

[0017] In one embodiment, the patterned area layer is selected from adhesive paste and printed mask layer. Adhesive paste and printed mask layer are functionally convenient ways to apply the patterned area.

[0018] In this regard, the patterned region layer should be interpreted as a local mask having a predetermined shape, which is positioned around the location of the defect in the dielectric polymer layer.

[0019] Those skilled in the art will appreciate that there are several alternative methods for gluing or printing the mask layer, such as surface treatment that prevents the electrode material from wetting or curing at specific locations; or chemical deposition that prevents the electrode material from wetting or curing at specific locations; or an electrode deposition process (precision spraying or printing) that is accurate enough to obtain the desired geometry.

[0020] In one embodiment, the step of producing the electrode layer as described above includes printing the electrode layer. The electrode layer can also be directly printed so that the area without the electrode layer surrounds the surface area position, and the surface area position itself is covered by the electrode patch. The printing of the electrode layer can be carried out in many ways known in the art.

[0021] In one embodiment, the patterned area layer as described above has an annular shape, and the patterned area layer is arranged centered on the surface area position. The annular shape is advantageous because the patterned area layer does not have any sharp corners that may cause local electric field enhancement. In one embodiment, the method further comprises curing the electrode layer after the printing step. The curing step after printing increases the durability of the electrode layer.

[0022] In one embodiment, the method comprises the step of filling the areas free of electrode layer material with a dielectric polymer material. The dielectric polymer will be able to isolate the defects from the surrounding electrode layer.

[0023] In one embodiment, the defect is an electrical breakdown defect, and the method as described above includes the steps of determining the surface area location of the electrical breakdown defect including: providing a conductive substrate; disposing a dielectric polymer layer having a second surface opposite to the first surface on the conductive substrate so that the first surface faces 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 on the first surface so that the first surface of the dielectric polymer layer is exposed to the applied high voltage.

[0024] The dielectric polymer layer is exposed to an electrical proof load test before being assembled into a generator ring or stack. Thus, when the entire layer has been tested under high electric fields (which may be higher than the electric fields used in operation), the material can operate reliably. Testing of the entire layer achieves high reliability of the DEAP device.

[0025] The conductive substrate can be a conductive carrier web or a metallized carrier web. The conductive substrate can be, for example, a carrier web made of polyethylene terephthalate (PET) that is metallized with a few nanometers of aluminum using a physical vapor deposition (PVD) process. A coating of 10 nm to 15 nm should be sufficient, resulting in a sheet resistance of about 5 ohms per square.

[0026] The movable electrode can be a movable cylinder that rolls over the film dielectric polymer layer. The cylinder allows the testing process to be continuous with a limited amount of electrical energy stored in the system because only that portion of the layer below the high voltage cylinder is tested. Preferably, the movable electrode is in contact with the dielectric polymer layer as it moves. In one embodiment, the movable electrode has a width of 50 cm. The conductive substrate is grounded. The dielectric polymer layer is discharged by two cylinders grounded on each side of the high voltage cylinder and rolling on the dielectric polymer layer.

[0027] In one embodiment, the method as described above includes locally generating an electrical breakdown defect in the dielectric polymer layer during exposure to a high voltage, and the method also includes optically or electrically detecting the location of the defect generated on the first surface, and determining the surface area location from the location of the defect. In this way, defects can be detected consistently, thereby reducing the probability of missing any defects. The dielectric polymer layer can be exposed to a high voltage several times to ensure that defects along the same line are not missed. After each test at a high voltage, the identified electrical breakdown defects can be covered with adhesive so that they are not subjected to the next high voltage test. As an alternative to optical or electrical detection, those skilled in the art will understand that mechanical detection or mechanical sensing is also possible.

[0028] In one embodiment, the method further comprises removing the layered structure of the dielectric polymer layer and the electrode layer from the conductive substrate. In this way, the layered structure can be used in a stack of layered structures.

[0029] In one embodiment, the generation of the electrode layer includes forming a conductive terminal on the dielectric polymer layer in communication with the electrode layer. The conductive terminal allows a voltage to be applied to the electrode layer.

[0030] In one embodiment, the method further comprises forming a stack of multiple removed layered structures on top of each other by gluing or bonding the dielectric polymer layer of one removed layered structure to the electrode layer of another adjacent removed layered structure in the stack. Having multiple layered structures on top of each other allows for greater energy generation compared to a single layered structure.

[0031] In one embodiment, the material of the electrode layer is selected from a conductive elastomer or a graphene-based elastic material. These materials meet the following requirements: elasticity - 100% minimum elongation at break - and sheet resistance: maximum 5 kΩ per square. The stiffness of the electrode layer is preferably lower than the stiffness from the dielectric layer, i.e. E(d).h(d)>E(e).h(e), where E and h are the Young's modulus and thickness of the dielectric layer (d) and the electrode layer (e), respectively.

[0032] According to one aspect of the present invention, and in accordance with the advantages and effects described herein, there is provided an electroactive polymer device comprising a plurality of dielectric polymer layers and a plurality of electrode layers, said dielectric polymer layers and said electrode layers being stacked on each other in an alternating order, wherein at least one electrode layer is an electrode layer comprising an area free of electrode layer material surrounding 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 isolating patch of electrode material.

[0033] The device is suitable for operation with electric fields greater than 1 V / μm (volts per micrometer), preferably greater than 10 V / μm, more preferably 50 to 200 V / μm.

[0034] According to one aspect of the present invention, and in accordance with the above advantages and effects, there is provided an adhesive tape for use in the method described herein, the adhesive tape comprising an annular shape with a central opening, and preferably comprising a non-adhesive tab. The diameter of the adhesive tape is preferably 25 mm to 50 mm, and has a central opening preferably of 10 mm to 20 mm. The adhesive tape is preferably made of PET or PE (polyethylene; polyethene).

[0035] The various aspects discussed in this patent can be combined to provide additional advantages. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0037] Figure 1 shows a schematic diagram of an electrical proof load test device used in one embodiment;

[0038] Figure 2 Shown is a top view of an adhesive tape according to one aspect of the present invention;.

[0039] Figure 3 shows a cross section of a dielectric polymer layer with adhesive paste manufactured by this method;

[0040] Figure 4 The electrode layer is deposited Figure 3 Components;

[0041] Figure 5 Shows the adhesive removed Figure 4 Components;

[0042] Figure 6 shows a cross-sectional view of a layered structure produced by this method, and

[0043] Figure 7 Shown is a cross section of an electroactive polymer device according to one aspect of the present invention.

[0044] The drawings are for illustration purposes only and are not intended to limit the scope or protection provided by the claims. DETAILED DESCRIPTION OF THE INVENTION

[0046] Other advantages, features and details of the invention will be explained in the following description of some of its embodiments.In the description reference is made to the accompanying drawings.

[0047] Figure 1 A cross section of a test device for locating any defects in a dielectric polymer (elastomer) layer 10 using an electric field is schematically shown. The test device comprises a conductive substrate 40, in this exemplary case a PET carrier web 41 having a conductive surface 42, which is formed by metallization with a few nanometers of aluminum using physical vapor deposition. The conductive surface 42 is electrically grounded. The dielectric polymer layer 10 is disposed on the conductive surface 42 (e.g., in a coated manner). A conductive cylinder 43 connected to a high voltage power supply (not shown) is rolled on the dielectric polymer layer 10. In this way, a uniform electric field is applied between the conductive surface 42 and the conductive cylinder 43 through the dielectric polymer layer 10. Wherever there is a weak point in the dielectric polymer layer 10, a dielectric breakdown will occur, resulting in a pinhole defect 30 across the thickness of the dielectric polymer layer 10. The weak point can be a small opening or thinned area in the dielectric polymer layer 10 caused by, for example, dirt, bubbles or contamination. The diameter of the pinhole caused by the breakdown is typically about 50 microns to 100 microns.

[0048] Figure 2 Schematically shows a top view of an adhesive tape 50 according to one aspect of the present invention. Figure 1 As found by the method shown in , the adhesive tape 50 is suitable for being placed around the pinhole. To this end, the adhesive tape 50 includes an annular shape 51 around the central opening 52, and a non-adhesive tab 53 for easy removal. The width w1 of the annular shape 51 (on 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 selected so that they are sufficient to electrically isolate the pinhole defect from the surrounding environment. Rounded edges are preferred to avoid sharp transitions that lead to electric field enhancement.

[0049] Figure 3 Schematically shows Figure 1 A cross section of a dielectric polymer layer 10 on a conductive substrate 40 is shown. Figure 2 The adhesive paste 50 is shown placed on top of the dielectric polymer layer 10, centered on the pinhole defect 30. Determining the precise surface area location 33 of the pinhole defect 30 can be accomplished, for example, by a high resolution camera. In addition, information from the high voltage power supply and / or the movable electrode 43 obtained during the high voltage exposure of the dielectric polymer layer can be used to determine the surface area location 33.

[0050] Figure 4 Schematically shows Figure 3 , but now the dielectric polymer layer 10 and adhesive paste 50 are coated with an electrode layer 20, which can be a conductive elastomer. The electrode layer 20 also completely covers the pinhole defect 30. Some electrode material can enter the pinhole defect 30.

[0051] Figure 5 Schematic diagram showing the removal of adhesive paste ( Figure 2 ), for example using a non-adhesive tab 53, which results in the removal of a portion of the electrode layer 20. This removal results in an annular region 32 that is now free of the electrode layer 20, and electrically isolates the 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 rest of the electrode layer 20.

[0052] Figure 6 Schematically shows Figure 5 A structure comprising a dielectric polymer layer 10 having pinhole defects 30 and an electrode layer 20 embedded in a stack of other layers forming a layered structure 1. Figure 1-5 The conductive substrate is peeled off. The dielectric polymer layers 11, 12, 10, 13, 14 are alternated with the electrode layers 21, 22, 20, 23, 24, and the electrode layers 21, 22, 20, 23, 24 are alternately offset to produce contacts with different polarities. The pinhole defect 30 is now glued to the electrode layer 23 on one side and to the conductive patch 31 on the other side. Gluing on both sides prevents any tearing or crack propagation originating from the pinhole defect 30, which is particularly important when the layered structure 1 is repeatedly stretched.

[0053] Figure 7 shows a cross section of an electroactive polymer device 2 comprising Figure 2 The layered structure 1 and the positive contact 3 and the negative contact 4 are configured so that the electrode layers 21, 22, 20, 23, 24 have positive and negative poles alternately. It is worth noting that the pinhole defect 30 and the area of ​​the dielectric polymer layer 10 surrounding the pinhole defect 30 are not exposed to the electric field because the electrode materials on both sides of the dielectric polymer layer 10 at the location of the pinhole defect 30 have the same polarity. Therefore, premature dielectric failure at the location of the pinhole defect 30 is prevented.

[0054] The present invention may be implemented in other specific forms without departing from the spirit or essential features of the present invention. The described embodiments are considered to be illustrative and not restrictive in all respects. Therefore, the scope of the present invention is indicated by the appended claims rather than the foregoing description. It is obvious to those skilled in the art that replacement and equivalent embodiments of the present invention can be envisioned and simplified to practice. All changes within the meaning and scope of the equivalents of the claims are included in their scope.

Claims

1. A method for manufacturing an electroactive polymer device, the electroactive polymer device comprising a layered structure, the layered structure comprising a dielectric polymer layer and an electrode layer, wherein the electrode layer is disposed on a surface of the dielectric polymer layer; The method comprises: providing the dielectric polymer layer; determining a surface area location of a defect on a first surface of the dielectric polymer layer; producing an electrode layer comprising an area free of electrode layer material surrounding the surface area location, The electrode layer comprises a patch of electrode material covering the surface region location and a remainder of the surface of the dielectric polymer layer surrounding the region free of electrode layer material, wherein the patch and the remainder are electrically isolated from each other.

2. The method according to claim 1, wherein the step of producing 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 remaining portion of the surface of the dielectric polymer layer exposed; depositing an electrode layer material over at least the surface region location and a remainder of the surface of the dielectric polymer layer; The patterned area layer is removed to produce the electrode layer including an area surrounding the surface area location that is free of the electrode layer material. 3 . The method of claim 2 , further comprising curing the electrode layer after removing the patterned region layer.

4. The method according to any one of claims 2 to 3, wherein the patterned area layer is selected from an adhesive paste and a print mask layer. The method according to claim 1 , wherein the step of producing an electrode layer comprises printing the electrode layer. The method of claim 5 , further comprising curing the electrode layer after the printing step.

7. The method according to claim 1, wherein: The region free of electrode layer material has a ring shape and is arranged with the surface region position as the center.

8. The method according to claim 1, wherein: The method further comprises the step of filling the areas free of electrode layer material with a dielectric polymer material.

9. The method of claim 1, wherein the defect is an electrical breakdown defect, and The step of determining the surface area location of the electrical breakdown defect comprises: providing a conductive substrate; disposing a dielectric polymer layer having a second surface opposite the first surface on the conductive substrate such that the first surface faces away from the conductive substrate; placing a movable electrode on or over said first surface; applying a high voltage between the movable electrode and the conductive substrate; The movable electrode is moved over the first surface to expose the first surface of the dielectric polymer layer to an applied high voltage.

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

11. The method of claim 9, wherein the layered structure of the dielectric polymer layer and the electrode layer is removed from the conductive substrate.

12. The method of claim 10, wherein the layered structure of the dielectric polymer layer and the electrode layer is removed from the conductive substrate.

13. The method of claim 1, wherein the generating of the electrode layer comprises forming conductive terminals on the dielectric polymer layer in communication with the electrode layer.

14. The method according to claim 11, wherein: The method further comprises forming a stack of a plurality of removed layer structures on top of each other by gluing or bonding the dielectric polymer layer of one removed layer structure to the electrode layer of another adjacent removed layer structure in the stack.

15. An electroactive polymer device comprising a plurality of dielectric polymer layers and a plurality of electrode layers, said dielectric polymer layers and said electrode layers being stacked on each other in an alternating order, wherein at least one electrode layer is an electrode layer comprising an area free of electrode layer material surrounding a surface area location of a defect in an adjacent dielectric polymer layer, and said surface area location of said defect is covered by an electrically isolated patch of said electrode material.

16. Adhesive bonding, characterized in that, The adhesive tape is applied according to the method of any one of claims 1 to 14 and comprises an annular shape with a central opening.

17. The adhesive strip of claim 16, wherein the adhesive strip further comprises a non-adhesive tab.

18. The adhesive tape of claim 16, wherein the adhesive tape is adapted to be placed on top of the dielectric polymer layer centered on the defect.

19. The adhesive tape of claim 17, wherein the adhesive tape is adapted to be placed on top of the dielectric polymer layer centered on the defect.

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