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), Ti ₃ C ₂ 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.
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