Hydrogels have been entensively explored for their intrinsic biocompatible and adhesive properties. However, limitations such as low viscosity, easy dehydration, and difficulty in peeling off the skin. Herein, we develop a hydrogel with a dual crosslinked network of gelatin and polyvinyl alcohol, which shows a unique thermally responsive reversible phase-change property between the flowing fluid state and the viscoelastic gel state. The enhanced hydrogel-based device can be steadily attached to the skin for reliable monitoring or quickly removed by controlling the temperature. Besides, the developed hydrogel exhibits ultra-thin, anti-drying, and self-healing properties. By introducing PEDOT: PSS and graphene dispersion, the hydrogel can be used as skin-mountable electrodes for high-fidelity electrocardiogram signal capture in the long term. By incorporating cobalt nanoporous carbon, a bilayer structure composed of triboelectric and conductive hydrogels is fabricated for non-contact sensing based on hydrogel-triboelectric nanogenerators. This work provides an idea for preparing viscosity-adjustable gels and a promising strategy for developing skin-mountable multifunctional sensors.

URL: https://www.sciencedirect.com/science/article/pii/S2211285525000813?via%3Dihub