Environmentally Resistant, Self-Adhesive, Antifreeze, and Moisturizing Conductive Hydrogels for Flexible Strain Sensors and Human-Motion Detection

Conductive hydrogels are promising candidates for flexible sensing applications owing to their intrinsic flexibility, strong adhesion, and excellent skin conformity, enabling reliable detection of both large-scale and subtle human motions. Nevertheless, conventional hydrogels are prone to water evaporation at high temperature and freezing below 0 °C, which severely compromise their conductivity and mechanical integrity. Herein, a multifunctional and environmentally resistant hydrogel (P(HEA-co-AM)) is developed via a one-pot polymerization method using 2-hydroxyethyl acrylate (HEA) and acrylamide (AM) monomers in a glycerol/water binary solvent, with Na+ serving as mobile charge carriers. The introduction of ionic pairs significantly enhanced ionic conductivity (30.2 ± 0.3 mS·cm–1 at 60 °C and 0.4 ± 0.02 mS·cm–1 at −40 °C) and ensured stable electrochemical responsiveness under extreme conditions. Benefiting from the strong hydrogen bonding of glycerol, the hydrogel exhibits remarkable antifreeze and moisturizing properties, together with outstanding stretchability (850 ± 5% strain, n = 3), high compressive strength (580 kPa), and robust adhesion. When employed as flexible strain sensors, the hydrogels precisely monitored joint movements and microexpressions, delivering stable electrical signals over a wide temperature range (−40 to 60 °C). This work highlights the synergistic effect of solvent–ion interactions in constructing durable, wide-temperature-tolerant hydrogels for next-generation wearable sensing devices.