# US 2025/0085176 A1 · Thin film sensor exhibiting enhanced sensitivity > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2025/0085176 A1 - Document ID: US20250085176A1 - Status: Published application - Kind: A1 - Application number: 18/292,774 - Filed: 2022-07-15 - Published: 2025-03-13 - Earliest claimed: 2021-07-26 - Assignees: Oerlikon Surface Solutions AG, PfäFfikon - Applicants: Oerlikon Surface Solutions AG, Pfäffikon - Inventors: Jukka KOLEHMAINEN; Sanna TERVAKANGAS; Juha HAIKOLA; Juergen BECKER; Astrid GIES; Christian SCHOLZ; Esa HAIKOLA - Web page: https://patentgrep.com/patent/US20250085176A1 ## CPC - G01L 1/18: using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material - G01L: MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE (weighing G01G) ## Abstract This invention relates to a coating system to be used as thin film sensor, comprising a piezoresistive sensor element, wherein the piezoresistive sensor element is a layer embedded in the coating system, wherein the coating system is deposited on a surface of a substrate, preferably the substrate being a component or a tool or a part of a component or a part of a tool, wherein the piezoresistive sensor element comprises at least one hydrogen free tetrahedral amorphous carbon coating doped with X, i.e. a ta-C:X coating layer, where X is one or more chemical elements selected from the elements groups 13 and 15 of the periodic table of elements, preferably X is one or more from B, Al, Ga, In, Tl, N and P, wherein the ta-C:X coating layer exhibits an anisotropic gage factor. ## Claims ### Claim 1 A coating system to be used as thin film sensor, comprising a piezoresistive sensor element, wherein the piezoresistive sensor element is a layer embedded in the coating system, wherein the coating system is deposited on a surface of a substrate wherein: the piezoresistive sensor element comprises at least one hydrogen free tetrahedral amorphous carbon coating doped with X, i.e. a ta-C:X coating layer, where X is one or more chemical elements selected from the elements groups 13 and 15 of the periodic table of elements, wherein the ta-C:X coating layer exhibits an anisotropic gage factor. ### Claim 2 (depends on 1) The coating system according to claim 1, wherein the ta-C:X coating layer has an anisotropic gage factor comprising a vertical gage factor and a longitudinal factor, where the vertical factor is at least ten times higher than the longitudinal gage factor. ### Claim 3 (depends on 1) The coating system according to claim 1, wherein the at least one ta-C:X coating layer exhibits: a hardness HIT determined by nanoindentation techniques of at least 29 GPa, an elastic modulus EIT determined by nanoindentation techniques of at least 300 GPa, a carbon content determined by SIMS analysis of at least 90 at, and a content of X determined by SIMS analysis of at least 2 at. ### Claim 4 (depends on 1) The coating system according to claim 1, wherein X comprises: nitrogen N, or phosphor P, or nitrogen N and phosphor P. ### Claim 5 (depends on 4) The coating system according to claim 4, wherein the nitrogen content in the of at least one ta-C:X coating layer is in a range from 2 at. % to 10 at. ### Claim 6 (depends on 4) The coating system according to claim 4, wherein X is nitrogen, i.e. ta-C-X is ta-C:N. ### Claim 7 (depends on 4) The coating system according to claim 4, wherein the N content in the ta-C:N coating layer in is a range from 6.5 at. % to 7.5 at. %. ### Claim 8 (depends on 1) The coating system according to claim 1, wherein the piezoresistive sensor element is contacted by electrically conductive connectors in such a manner that the piezoresistive sensor element provides an electrical signal as a function of at least the strain or temperature from the substrate surface. ### Claim 9 (depends on 1) The coating system according to claim 1 wherein the coating system comprises an under electrical insulating layer provided between the substrate surface and the piezoresistive sensor element. ### Claim 10 (depends on 1) The coating system according to claim 1, wherein the coating system comprises an adhesive layer provided directly onto the substrate surface. ### Claim 11 (depends on 1) The coating system according to claim 1, wherein the coating system comprises an upper electrical insulating layer provided directly onto the piezoresistive sensor element. ### Claim 12 (depends on 1) The coating system according to claim 1, wherein the coating system comprises at least one functional layer ### Claim 13 (depends on 1) A thin film sensor comprising a coating system according to claim 1 to be used for determining at least temperature or strain. ### Claim 14 (depends on 13) A component, or a tool comprising a thin film sensor according to claim 13, said thin film sensor incorporated in the component or tool for determining at least temperature or strain. ### Claim 15 (depends on 1, 13) A method for producing a coating system according to claim 1, or for producing a thin film sensor according to claim 13, wherein the at least one ta-C:X coating layer is deposited by using PVD or PA-CVD techniques. ### Claim 16 (depends on 1) The coating system according to claim 1, wherein X is one or more from B, Al, Ga, In, TI, N and P. ### Claim 17 (depends on 1) The coating system according to claim 1, wherein the longitudinal gage factor in a range from 4 to 20, and the vertical gage factor in a range from 100 to 450. ### Claim 18 (depends on 1) The coating system to claim 1, wherein the at least one functional layer is a DLC coating layer, or any other coating layer exhibiting specific tribological properties depending of the use. ### Claim 19 (depends on 3) The coating system according to claim 3, wherein the at least one ta-C:X coating layer exhibits: a hardness HIT determined by nanoindentation techniques in a range from 30 GPa and 45 GPa, an elastic modulus EIT determined by nanoindentation techniques in a range from 330 GPa and 430 GPa, a carbon content determined by SIMS analysis in a range from 91 at. % and 98 at. %, and a content of X determined by SIMS analysis in a range from 2 at. % to 20 at. %. ### Claim 20 (depends on 5) The coating system according to claim 5, wherein the nitrogen content in the of at least one ta-C:X coating layer is in a range from 6.5 at % to 8.5 at. %.