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

Abstract

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.