Interfaceless Strain and Pressure-Sensitive Stretchable Capacitor Based on Self-Bonding and Surface Morphology Control of a Reversibly Crosslinkable Silicone Elastomer

A typical capacitive mechanical sensor implemented using a layer of soft dielectric polymer sandwiched between two flexible electrodes, where the capacitance is formed, suffers from unintended buckling instability upon repeated stretch-and-release owing to different mechanical characteristics of constituent materials and unstable interfaces. Here, a stretchable, healable, and transparent strain/pressure-sensitive capacitor is successfully fabricated by hybridizing Ag nanowires (AgNWs) with a polydimethylsiloxane containing maleimide-derived Diels-Alder (DA) adducts as reversible crosslinkers. AgNWs formed on the surface of the cured polymer sheet are impregnated under the surface of the film by utilizing the vaporized solvent-assisted retro-DA reaction. Two identical films with fully impregnated AgNWs under the polymer surface are subjected to lamination with the insulated areas facing each other to implement a sandwich-structure with a centering dielectric layer. Owing to the retro-DA and reversible crosslinking during heating, two films in contact are fully integrated as if the architecture is originally made of a single film. The sensitivity to pressure under the stretching condition increases by about 320% compared to that without stretching.