Transparent, Antifreezing, Ionic Conductive Carboxymethyl Chitosan Hydrogels as Multifunctional Sensors

By a simple strategy of immersion in a CaCl2 solution, carboxymethyl chitosan hydrogels exhibited ultralow-temperature freezing resistance below −50 °C. In addition, the introduction of electrolyte ions endowed the hydrogels with electrical conductivity, showing stable and reversible sensitivity to human activity, such as finger bending, pressing, and pharyngeal swallowing. The conductive carboxymethyl chitosan hydrogels could even be assembled into a two-dimensional integrated array of contact sensors, which successfully perceived the contour and pressure distribution of an object with a certain resolution. These transparent biological-based antifreezing conductive hydrogels are promising to find applications in integrated wearable sensing devices under extremely low temperature environments.