Hydrogel from Chrome Shavings as a Sustainable, Highly Sensitive Ionic Skin for Pressure Sensing

Ionic hydrogel skin with high sensitivity and wide sensing range is currently urgently desired in artificial intelligence and human–machine interactions. Surface relief and inner gel structure are the decisive factors of high-sensitivity ionic hydrogel capacitive pressure sensors (CPSs). Nevertheless, it is usually difficult to process precise structures on hydrogels due to their poor machinability properties. Here, inspired by the Merkel cell structure, we designed and constructed the fiber hybrid gel with a synapse surface and a fiber-embedded gel pore wall by chrome shavings. A novel hydrogel preparation process, including pre-construction of the leather collagen fiber film, transformation of the film to the 3D fiber skeleton, and subsequent gelation conversion, could fully preserve and utilize the natural fiber structure. The as-prepared ionic hydrogel CPS owns high sensitivity and remarkable mechanical stability. The sensitivity of the device can reach 5.32 kPa–1 below 0.8 kPa and remain larger than 2.6 kPa–1 over a broad-range pressure from 0 to 7.5 kPa. This work offers a novel, simple approach from a bionic perspective to construct the high-sensitivity ionic hydrogel CPSs via low-cost leather chrome shavings.