Connecting a flexible circuit to other structures
One example provides a circuit structure comprising a liquid metal conductive path enclosed in an encapsulant, a polymer circuit support comprising a polymer having a functional species available for a condensation reaction, and a cross-linking agent covalently bonding the encapsulant to the polymer circuit support via the functional species.
1. A method of electrically connecting and covalently bonding a flexible circuit structure to a polymer circuit support, the flexible circuit structure comprising a flexible interconnect including a gallium-containing liquid metal conductor encapsulated within a siloxane-based encapsulant comprising an embedded conductor, the method comprising:
activating a surface of the polymer circuit support;
applying a cross-linking agent to the surface of the polymer circuit support after activating the surface, the cross-linking agent comprising a siloxane functional group and a second functional group bound to the siloxane functional group, the second functional group covalently bonding to the activated surface of the polymer circuit support;
activating the siloxane functional group of the cross-linking agent; and
covalently bonding the siloxane-based encapsulant to the activated siloxane functional group of the cross-linking agent, thereby connecting the gallium-containing liquid metal conductor within the siloxane-based encapsulant to a conductor on the polymer circuit support via the embedded conductor.
2. The method of claim 1 , wherein activating the surface of the polymer circuit support comprises exposing the surface of the polymer circuit support to one or more of an oxygen plasma, an air plasma, and an argon plasma, and wherein activating the siloxane functional group of the cross-linking agent comprises exposing the siloxane functional group of the cross-linking agent to one or more of oxygen plasma, air plasma, and argon plasma.
3. The method of claim 1 , further comprising, prior to bonding the siloxane-based encapsulant to the activated siloxane functional group of the cross-linking agent, activating the siloxane-based encapsulant by exposing the siloxane-based encapsulant to one or more of an oxygen plasma, an air plasma, and an argon plasma.
4. The method of claim 1 , further comprising forming an electrical coupling between the gallium-containing liquid metal conductor of the flexible circuit structure and a circuit element of the polymer circuit support.
5. The method of claim 4 , wherein the embedded conductor comprises embedded magnetic particles.
6. The method of claim 4 , wherein the embedded conductor comprises embedded nanowires.
7. The method of claim 1 , wherein activating the surface of the polymer circuit support comprises activating a surface of a polycarbonate, a polyethylene terephthalate, a polyvinyl chloride, or a polyimide circuit support.
8. The method of claim 1 , wherein applying the cross-linking agent to the surface of the polymer circuit support comprises applying poly[dimethylsiloxane-co-(3-aminopropyl)methylsiloxane].