# US 12,180,380 B2 · Highly conductive, printable ink for highly stretchable soft electronics and highly conductive, ultra-stretchable conductors obtainable therefrom > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,180,380 B2 - Document ID: US12180380B2 - Status: Granted - Kind: B2 - Application number: 17/431,510 - Filed: 2020-02-14 - Published: 2022-02-17 - Granted: 2024-12-31 - Earliest claimed: 2019-03-11 - Assignees: Karlsruher Institut für Technologie - Applicants: Karlsruher Institut FüR Technologie - Inventors: Hongye Sun; Norbert Willenbacher - Web page: https://patentgrep.com/patent/US12180380B2 ## CPC - C09D 11/52: Electrically conductive inks - C09D 11/033: characterised by the solvent - C09D 11/037: characterised by the pigment - C09D 11/102: containing macromolecular compounds obtained by reactions other than those only involving unsaturated carbon-to-carbon bonds - C09D: COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR (cosmetics A61K; processes for applying liquids or other fluent materials to surfaces, in general, B05D; staining wood B27K5/02; glazes or vitreous enamels C03C; natural resins, French polish, drying-oils, driers, turpentine, per se, C09F; polishing compositions other than French polish, ski waxes C09G; adhesives or use of materials as adhesives C09J; materials for sealing or packing joints or covers C09K3/10; materials for stopping leaks C09K3/12; processes for the electrolytic or electrophoretic production of coatings C25D) ## Abstract The present invention relates to highly conductive, printable inks for highly stretchable soft electronics, a process for their manufacture as well as highly conductive, ultra-stretchable conductors obtainable therefrom. ## Claims ### Claim 1 A highly conductive, printable ink, comprising: (i) 1.5 to 21.0 vol % of conductive hydrophobic silver particles, with respect to the total volume of ink, as conductive solid phase, (ii) a liquid primary phase comprising, as a polymer base, a thermoplastic polyurethane (TPU) dissolved in an organic polar solvent, wherein the volume content of TPU in the organic polar solvent is in the range of 25% to 50%, wherein the liquid primary phase takes up 76.90 to 98.49 vol % with respect to the total volume of ink, (iii) a liquid secondary phase based on an ionic liquid, with a volume content in the range of 0.0015 to 2.1 vol %, with respect to the total volume of the ink, while the volume ratio ρ between said liquid secondary phase and said conductive solid phase falls in the range of 0.001 to 0.1, wherein the liquid secondary phase is immiscible with the liquid primary phase and does not wet the conductive solid phase, so that the three-phase system creates a capillary suspension. ### Claim 2 (depends on 1) The ink according to claim 1, wherein the conductive hydrophobic silver particles have a medium particle size d50 of 0.1 to 50 μm, measured by laser diffraction in accordance with DIN EN 725-5, ISO 13320. ### Claim 3 (depends on 1) The ink according to claim 1, wherein the thermoplastic polyurethane is selected from polyester-based or polyether thermoplastic polyurethane. ### Claim 4 (depends on 1) The ink according to claim 1, wherein the thermoplastic polyurethane is characterized by having an elongational failure strain εr ranging from 50% to 2500%. ### Claim 5 (depends on 1) The ink according to claim 1, wherein the polar solvent of the liquid primary phase is selected from the group consisting of tetrahydrofuran (THF), dimethyl formamide (DMF), dimethyl sulfoxide (DMSO), dimethylacetamide (DMAc) or combinations thereof. ### Claim 6 (depends on 5) The ink according to claim 5, wherein the polar solvent is mixed with a co-solvent selected from acetone, methyl ethyl ketone (MEK), cyclohexanone, toluene or ethyl acetate (ETAc). ### Claim 7 (depends on 1) The ink according to claim 1, wherein the ionic liquid contains a substituted or unsubstituted imidazolium cation, wherein the imidazolium cation of the salt is preferably in the 1- and 3-position or in the 1-, 2- and 3-position with (C1-C6) alkyl groups, and the anion of the ionic liquid is a halide, perchlorate, pseudohalide, sulfate, phosphate, alkyl phosphate and/or a C1-C6 carboxylate ion. ### Claim 8 (depends on 7) The ink according to claim 7, wherein the imidazolium cation is selected from the 1-ethyl-3-methylimidazolium, 1,3-dimethylimidazolium or 1-butyl-3-methylimidazolium cation. ### Claim 9 (depends on 1) The ink according to claim 1, wherein the ionic liquid contains 1-butyl-3-methylimidazolium iodide, 1-butyl-3-methylimidazolium chloride, or 1-butyl-3-methylimidazolium bromide: ### Claim 10 (depends on 1) A process for producing a highly conductive and printable ink according claim 1, comprising: mixing of (i) 1.5 to 21.0 vol % of conductive hydrophobic silver particles, with respect to the total volume of ink, as conductive solid phase, (ii) a liquid primary phase comprising, as a polymer base, a thermoplastic polyurethane (TPU) dissolved in an organic polar solvent, wherein the volume content of TPU in the organic polar solvent is in the range of 25% to 50%, wherein the liquid primary phase takes up 76.90 to 98.49 vol % with respect to the total volume of ink, (iii) a liquid secondary phase based on an ionic liquid, with a volume content in the range of 0.0015 to 2.1 vol %, with respect to the total volume of the ink, while the volume ratio ρ between said liquid secondary phase and said conductive solid phase falls in the range of 0.001 to 0.1, wherein the liquid secondary phase is immiscible with the liquid primary phase and does not wet the conductive solid phase, so that the three-phase system creates a capillary suspension. ### Claim 11 (depends on 10) The process according to claim 10, wherein the silver particles are dispersed in the liquid primary phase by mechanical stirring, followed by adding the liquid secondary phase and a subsequent mixing step to break up the liquid secondary phase into droplets. ### Claim 12 (depends on 1) A process for producing highly stretchable soft electronics in the form of an elastic composite by applying the ink according to claim 1 on a soft substrate, preferably by means of dispensing, screen printing, slot die coating, spraying or direct ink writing, and then evaporating the solvents, to yield a stretchable and deformable electrical device. ### Claim 13 (depends on 12) A highly conductive, stretchable conductor obtainable by the process of claim 12, comprising: (i) 5 to 30 vol %, preferably 8 to 20 vol %, of conductive hydrophobic silver particles, with respect to the resulting solid conductor, as conductive solid phase, (ii) 67 to 94.99 vol %, preferably 78.80 to 91.99 vol %, of thermoplastic polyurethane (TPU), and (iii) a liquid (secondary) phase based on an ionic liquid, with a volume fraction of 0.005 to 3.0 vol %, preferably 0.08 to 1.20 vol %, with respect to the resulting solid conductor, while the volume ratio ρ between said liquid secondary phase and said conductive solid phase falls in the range of 0.001 to 0.1. ### Claim 14 (depends on 1) An article formed from the highly conductive and printable ink according to claim 1 sensors, soft robotics, wireless devices, flexible solar cells, or soft electronics. ### Claim 15 (depends on 14) The article of claim 14, wherein the article is selected from a sensor, a soft robotic, a wireless device, a flexible solar cell, or a soft electronic.