Ultra-fast cryogenic self-healing ionic hydrogel for flexible wearable bioelectronics

Anti-freezing and self-healing hydrogels have been developed extensively for their irreplaceable advantages in flexible bioelectronics. However, the self-healing performance of hydrogels is extremely inefficient or even disappears in cryogenic environments, resulting in device damage and economic loss. Here, we proposed a ultrafast cryogenic self-healing ionic hydrogel (ASCL) based on aldehyded hyaluronic acid (AHA) with the synergistic effect of dynamic Schiff base bonds and diselenide bonds. With the addition of lithium chloride (LiCl), the ASCL hydrogel can be rapidly self-healed within 5 min at a cryogenic temperature of-20 degrees C. The mechanism of LiCl for enhancing the anti-freezing property of hydrogels was demonstrated by molecular dynamics simulations and a series of tests at cryogenic temperatures. ASCL hydrogels exhibited good flexibility and high electrical conductivity of 0.27 S/m at cryogenic temperatures. The assembled ASCL hydrogel strain sensors and pressure sensors enable sensitive detection of various human motions at-20 degrees C, which possess a gauge factor of 1.07 and a sensing sensitivity of 0.29 kPa- 1 , respectively. This work provides a new paradigm for developing flexible wearable hydrogel bioelectronics in extreme environments.