A flexible wearable sensor based on the multiple interaction and synergistic effect of the hydrogel components with...

To meet the increasing demand for wearable sensor in special environment such as low temperature or underwater, a multifunctional ionic conducting hydrogel (Gel/PSAA-Al³⁺ hydrogel) with anti-freezing and low swelling for human motion detection and underwater communication was prepared using gelatin (Gel), [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide (SBMA), acrylamide (AAm), acrylic acid (AAc), and AlCl₃. Due to reversible hydrogen bonding, electrostatic interactions and metal coordination crosslinking between the polymer networks, the resulting Gel/PSAA-Al³⁺ hydrogels present low swelling property in water and exhibit large tensile properties (~1050 %), high tensile strength (~250 kPa) and excellent fatigue resistance. In addition, the hydration capacity of SBMA and AlCl₃ endows the Gel/PSAA-Al³⁺ hydrogel fantastic anti-freezing (-31.58 °C) and water retention properties. Moreover, the electrostatic interaction between SBMA and AlCl₃ due to the ion hopping mechanism endows the hydrogel with excellent ionic conductivity (6.38 mS/cm). The Gel/PSAA-Al³⁺ hydrogel sensors present good biocompatibility and provide a wide operating range (0 %-1050 %), fast response time (229 ms) and recovery time (248 ms), high sensitivity (GF = 1.61) and excellent stability for detecting large and small body movements. The Gel/PSAA-Al³⁺ hydrogel shows potential applications as a wearable sensor for communication at low temperature or underwater.