Highly sensitive, anti-freezing and stretchable hydrogels with modified MXene for multifunctional applications

Hydrogels have emerged as ideal materials for sensor fabrication due to their tunable mechanical properties, flexibility, and biocompatibility. However, their high-water content makes them prone to freezing at low temperatures, which compromises their conductivity and mechanical integrity, limiting their use in cold environments. To address this issue, we present a novel hydrogel system consisting of a polyacrylamide (PAM) backbone, a binary solvent system of water and ethylene glycol (EG), and functional materials including polyvinyl alcohol (PVA) and modified MXene. The addition of modified MXene as a conductive filler significantly enhances the hydrogel's conductivity, enabling it to maintain its performance even at low temperatures. Furthermore, the introduction of EG effectively lowers the freezing point of the hydrogel to -36.9 °C, ensuring robust frost resistance. The resulting hydrogel not only shows exceptional low-temperature stability but also exhibits high sensitivity. Moreover, the hydrogel demonstrates rapid responsiveness and high accuracy when being integrated as sensors to detect human motion and ammonia concentrations. These results highlight the potential of MXene-enhanced hydrogels for applications in freshness detection of raw meat and human motion tracking, particularly in cold environments.