Facile synthesis of ultratough conductive gels with swelling and freezing resistance for flexible sensor applications

The application of flexible hydrogel sensors in extreme environments, such as low temperatures, underwater, or significant mechanical deformations, poses considerable challenges. Here, we present a simple one-pot method to fabricate ultra-tough, swelling- and freezing-resistant conductive organohydrogels without external conductive and freeze-resistant fillers. During gelation, by-products (C₆H₁₅NHCl, KCl) provide both conductivity and antifreeze properties, thus eliminating compatibility issues and dispersion challenges associated with external fillers. The resulting gel exhibits super toughness, with tensile strength reaching 10.2 MPa and stretchability up to 800% in the dry state. Following covalent crosslinking, the gel demonstrates excellent anti-swelling properties, with a swelling ratio of only 15.4% after 24 h of water immersion, while maintaining a tensile strength of 5.8 MPa and an elongation of up to 1000%. When fabricated into flexible sensors, these gels display stable electrical responsiveness and desired Gauge Factor (0.58-2.25), effectively detecting limb movements. Furthermore, the gel's superior resistance to freezing and swelling ensures reliable signal stability under both - 20 °C and underwater conditions. These combined properties render the conductive gel a promising candidate for flexible sensing components in robotic and bionic applications.