Low-temperature adaptive conductive hydrogel based on ice structuring proteins/CaCl2 anti-freeze system as wearable strain and temperature sensor.

Conductive hydrogels as wearable devices meet the basic demands of mechanical flexibility and smart sensing. However, achieving anti-freeze property in conductive hydrogels is still challengeable. Here, a novel anti-freezing system based on ice structuring proteins and CaCl2 was introduced to enable a conductive hydrogel with low-temperature adaptability. Both formation of ice nuclei and ice growth of the hydrogel at sub-zero temperature could be inhibited. Supported by the anti-freeze system, the hydrogel revealed good flexibility (890% at -20 °C), recovery and conductivity (0.50 S/m at -20 °C) at both room temperature and sub-zero temperature. The low-temperature adaptability enabled the hydrogel to be used as strain and temperature sensors at both room temperature and sub-zero temperature. The anti-freeze system in this work is expected to open up a new avenue to promote the conductive hydrogel with low-temperature adaptability.