MULTI-LAYER STRUCTURE, SYSTEM, USE AND METHOD

Abstract

The invention relates to a multi-layer structure having at least one flexible backing layer, at least one electrically insulating layer, and at least one electrically conductive layer, the electrically insulating layer being arranged between and connected to the backing layer and the electrically conductive layer, at least the backing layer being able to be elongated by at least 0.5% and comprising a shape memory material that is adapted to transmit restoring forces to mend cracks in the electrically insulating layer.

Claims

1. A multi-layer structure having at least one flexible backing layer, at least one electrically insulating layer, and at least one electrically conductive layer, the electrically insulating layer being arranged between and connected to the backing layer and the electrically conductive layer, at least the backing layer being able to be elongated by at least 0.5% and comprising a shape memory material which is adapted to transmit restoring forces to mend cracks in the electrically insulating layer.

2. The multi-layer structure according to claim 1, wherein the backing layer, the electrically insulating layer and the electrically conductive layer are together able to be elongated by at least 0.5%.

3. The multi-layer structure according to claim 1, wherein Van der Waals forces act between the boundary layers of the different material layers.

4. The multi-layer structure according to claim 1, wherein the material of the backing layer is selected from the group Nitinol, beta titanium, NiTi alloys, NiTiCu alloys, NiTiX alloys and polymers.

5. The multi-layer structure according to claim 1, wherein the material of the electrically insulating layer is selected from the group SiO2, SiO, SiOx, Al2O3 TiO2 NbO, NbO2, Nb2O5 TaO, TaO2, Ta2O5 ZrO2 (stabilized with (Y, Ca, Mg, Ce, Al, Hf) oxides) or from the group AlN TiN, 1:1 ratio may differ Si3N4 TaN, (there are also Ta2N, Ta2N3, Ta3N5, Ta4N5, Ta5N6) or from the group SiC.

6. The multi-layer structure according to claim 5, wherein additions are selected from the group Y2O3 WO2 MoO3 MoO2 ZnO MgO CaO Na2O P2O5 Fe2O3.

7. The multi-layer structure according to claim 1, wherein the material of the electrically insulating layer comprises a bioglass, in particular having the composition 45% by weight SiO2, 24.5% by weight CaO, 24.5% by weight Na2O, and 6.0% by weight P2O5.

8. The multi-layer structure according to claim 1, wherein the material of the electrically conductive layer is selected from the group NiTi alloys, PtIr alloys, Ta and alloys thereof, Pt and alloys thereof, Au and alloys thereof, Ag and alloys thereof, polymeric materials and carbon-containing materials.

9. The multi-layer structure according to claim 1, wherein the layer thickness of the electrically insulating layer is between 1 nm and 8 μm.

10. A system having a multi-layer structure according to claim 1 and a mechanical actuator which is connected to the multi-layer structure for the elongation of the multi-layer structure.

11. A use of the multi-layer structure according to claim 1, in a medical, bioelectronic implant, in particular for the electrical detection and stimulation of biological tissue, in a sensor or BioMEMS as an electrically insulated conducting path, for the detection of biological signals, in medical, industrial and lifestyle applications as an electrically insulated conducting path for the transmission of electrical signals, voltages or currents, in connection plugs and connection connectors as an electrically insulated connection, in connections to implants and wearables as an electrically insulated connection.

12. A method for self-mending of a multi-layer structure according to claim 1, in which the multi-layer structure is elongated by at least 0.5%.

13. The method according to claim 10, wherein the multi-layer structure is subjected to an alternating load for elongation.

14. A method for operating a multi-layer structure according to claim 1, in which an electrical voltage is applied to the electrically conductive layer and the multi-layer structure is subjected to an alternating load, in which the multi-layer structure is elongated by at least 0.5%, the elongation being adjusted such that a continuous current flows through the electrical conductor during the alternating stress or that the current through the electrical conductor is interrupted according to the frequency of the alternating stress during the alternating stress.

15. The method according to claim 11, wherein the backing layer has a residual elongation of at most 1% after loading.

Description

[0028] The invention is described below with reference to exemplary embodiments and with reference to the accompanying schematic drawings with further details.

[0029] These show

[0030] FIG. 1 a cross-section through a multi-layer structure having a backing layer, an electrically insulating layer and an electrically conductive layer according to an embodiment of the invention;

[0031] FIG. 2 a cross-section through a multi-layer structure according to an embodiment according to the invention before application of a load, during the load and after the load; and

[0032] FIG. 3 a diagram showing the curve of the resistance as a function of an alternating load over time.

[0033] FIG. 1 shows a cross-section through a multi-layer structure according to an embodiment of the invention. This can be, for example, a flexible, electrically insulated connection, which can generally be referred to as a multi-layer device or as a multi-layer system. The multi-layer structure forms a central component of the multi-layer system. An example of a multi-layer system is a multi-channel connector. The multi-layer structure shown is preferably used in the medical field. Other applications are possible.

[0034] Examples of such applications are applications [0035] in a medical, bioelectronic implant, in particular for the electrical detection and stimulation of biological tissue, [0036] in a sensor or BioMEMS as an electrically insulated conducting path, [0037] for the detection of biological signals, [0038] in medical, industrial and lifestyle applications as an electrically insulated conducting path for the transmission of electrical signals, voltages or currents, [0039] in connection plugs and connection connectors as an electrically insulated connection, [0040] in connections to implants and wearables as an electrically insulated connection.

[0041] The multi-layer structure according to FIG. 1 is constructed in three layers. An electrically insulating layer 11 is applied to a backing layer 10. An electrically conductive layer 12 is applied to the electrically insulating layer 11. The electrically conductive layer 12 is electrically insulated from the backing layer 10 by the electrically insulating layer 11. In the example according to FIG. 1, the electrically conductive layer 12 is encased by the electrically insulating layer 11, so that both the side facing the backing layer 10 and the side of the electrically conductive layer 12 facing away from the backing layer 10 are electrically insulated.

[0042] The multi-layer structure can have a plurality of electrically insulating layers 11 and electrically conductive layers 12 in sandwich construction or alternately one above the other. The electrically conductive layer 12 forms conducting paths which are interconnected for the function of the multi-layer structure or the corresponding system.

[0043] The backing layer 10 is made from a shape memory material. A nickel-titanium alloy is used for this in the example according to FIG. 1. Other shape memory materials are possible.

[0044] The material of the backing layer can be selected, for example, from the group [0045] Nitinol, [0046] beta titanium, [0047] NiTi alloys, [0048] NiTiCu alloys, [0049] NiTiX alloys and [0050] polymers

[0051] without being limited to this.

[0052] The backing layer can be elongated by at least 0.5%. Specifically, the entire multi-layer structure can be elongated by 0.5%. A corresponding elongation causes a phase transformation in the backing layer which is indicated by tension, so that corresponding forces, that is, restoring forces, are transmitted from the backing layer 10 to the electrically insulating layer 11. Any cracks formed in the electrically insulating layer 11 are eliminated or mended by these forces. Complete elimination is not necessary. It suffices when the electrically insulating layer 11 has fewer cracks after loading than before loading.

[0053] In the optimal case, the electrically insulating layer 11 is free of cracks before loading. During and after the loading, any cracks are suppressed or mended by the forces generated by the backing layer 10.

[0054] The backing layer 10 is flexible.

[0055] As can be seen from FIG. 1, the layer thickness of the backing layer 10 is greater than the layer thickness of the electrically insulating layer 11 and the electrically conductive layer 12 together. Other conditions are possible. For example, the layer thickness of the electrically insulating layer 11 is 600 nm, that is, the layer thickness between the electrically conductive layer 12 and the backing layer 10 is 600 nm. The layer thickness of the electrically conductive layer is 300 nm in this exemplary embodiment. The layer thickness of the insulator on the top side or on the side of the electrically conductive layer 11 facing away from the backing layer 10 is 300 nm in the embodiment. The layer thickness of the backing layer 10 can be 30 μm, for example. Other layer thicknesses are possible.

[0056] In general, the layer thickness of the electrically insulating layer 11 can be between 1 nm and 8 μm.

[0057] Reference is made to claims 5 to 8 regarding the materials of the electrically insulating layer 11 and the electrically conductive layer 12. Other materials are possible.

[0058] FIG. 2 shows a cross-section through a multi-layer structure according to an example according to the invention. The upper illustration in FIG. 2 shows a cross-section through the individual layers before they are loaded. The middle representation shows the individual layers during the loading. The lower illustration shows the individual layers after the loading. As a result, the layers during and after loading essentially correspond to the crack-free layers before loading. There is practically no difference. This is due to the self-mending effect of the multi-layer structure according to the example according to the invention.

[0059] FIG. 3 shows, based on a diagram, two different methods for operating a multi-layer structure according to an example according to the invention, for example, in the context of one of the above uses. The method is based on the fact that the multi-layer structure is subjected to an alternating load, so that there is a continuous self-mending effect, as described above.

[0060] Method A is a permanent and continuous electrical connection. The electrical conducting path on the insulator changes the electrical resistance under alternating loads. The resistance increases with increasing elongation, and the resistance decreases with decreasing elongation of the backing substrate. However, the insulation and electrical conduction are continuously present and can be subjected to permanent loads.

[0061] Method B results in a discrete electrical connection. The electrical connection is interrupted periodically, namely at the frequency of the alternating load. When a critical elongation value is exceeded, the connection is broken. If the elongation falls below this critical value, the electrical connection is present again and continuously. These processes are practically infinitely reproducible.

[0062] Possible manufacturing processes are: [0063] physical vapor deposition (PVD), including magnetron sputter deposition [0064] chemical vapor deposition (CVD), including atomic layer deposition, PECVD, [0065] thermal deposition

[0066] A shaping of the multi-layer structure by thermomechanical heat treatment is possible. This can be done, for example, by crystallization of the amorphously deposited shape memory material under mechanical load by heat treatment in a high vacuum furnace.