Skin‐Inspired, Multifunctional, and 3D‐Printable Flexible Sensor Based on Triple‐Responsive Hydrogel for Signal Conversion in Skin Interface Electronics Health Management

Hydrogel-based flexible electronic components have become the optimal solution to address the rigidity problem of traditional electronics in health management. In this study, a multipurpose hydrogel is introduced, which is formed by combining a dual-network consisting of physical (chitosan, polyvinyl alcohol (PVA)) and chemical (poly(isopropyl acrylamide (NIPAM)-co-acrylamide (AM))) cross-linking, along with signal conversion fillers (eutectic gallium indium (EGaIn), Ti₃C₂ MXene, polyaniline (PANI)) for responding to external stimuli. Multiple sensing of dynamic and static signals is permissible for it. The strain sensor based on the hydrogel exhibits up to a 1000% resistance change within a 400% stretch range, and significant capacitance variations are observed upon touch. The temperature sensor yields a sensitivity of ≈-2.9% °C^-1 at 20-40 °C and ≈65% °C^-1 at 0-20 °C. The pH sensor responds with a sensitivity of near -13.68 mV pH^-1. A paper-based triboelectric nanogenerator can be assembled to collect action energy at 83 mW m^-2. The skin contact interface is kept in good condition owing to its 3D-printability, controllable antibacterial properties, along high cell survival rate. This multifunctional hydrogel holds promise in facilitating the integration of diagnosis and maintenance.