Anti-freezing conductive hydrogels with exceptional mechanical properties and stable sensing performance at -30 °C

Conductive hydrogels with stable sensing performance are highly required in soft electronic devices. However, these hydrogels tend to solidify and experience structural damage at sub-zero temperatures, leading to material breakdown and device malfunction. The main challenge lies in effectively designing the micro/nano-structure to enhance mechanical properties and stable strain sensing while preventing freezing in hydrogels. Here, we present a rapid strategy for developing a MXene bridging double-network structure-based strain sensor using polyacrylamide and agar hydrogels that can maintain stable functionality even at an extremely low temperature of -30 °C. By incorporating MXenes as a catalyst to expedite free radical polymerization, we achieve outstanding mechanical and strain sensing properties at room temperature (a high response range of 1000%, a response signal linearity of 0.998, and a gauge factor (GF) value of 1.41). This sensing performance surpasses those reported for many other hydrogels. Importantly, we also observe that the stable micro-nanostructure in the hydrogel at an extreme temperature of approximately -30 °C results in exceptional strain-detection performance (a stable response range of up to 250%) with a linearity of 0.995 and a GF value of 1.25 due to its remarkably low freezing point (<-80 °C). These findings highlight the application of our hydrogel-based tactile sensor in low-temperature environments.