A tough, anti-freezing, and low-dehydration rate gelatin hydrogel with inverse temperature-dependent ionic conductivity

Flexible electronics based on soft hydrogels have garnered significant attention due to their superior mechanical durability, conductivity, freezing tolerance, and low dehydration rates. Moreover, hydrogels often exhibit a substantial decrease in conductivity at low temperatures despite their advantageous properties and adaptability. For applications requiring consistent performance under colder conditions, there is a pressing need to devise a strategy that ensures hydrogels maintain high conductivity even at reduced temperatures. This study introduces an innovative strategy for developing a gelatin-based hydrogel that exhibits inverse temperature-dependent ionic conductivity, substantial mechanical toughness, freezing tolerance, and minimal dehydration. Treating the gelatin hydrogels with composite salt solutions, containing anti-freezing acetate and chloride salts, notably increased the ionic conductivity of the hydrogel from 47.2 mS cm⁻¹ to 62.5 mS cm⁻¹ as the temperature decreased to approximately 5 °C. Excellent conductivity of 52.1 mS cm⁻¹ was observed even at −27 °C. The proposed hydrogel can be used in flexible electronics.