MXene reinforced organohydrogels with ultra-stability, high sensitivity and anti-freezing ability for flexible strain sensors

Hydrogels combining good biocompatibility and super flexibility have attracted tremendous interest in flexible sensors. Nevertheless, they always suffer from poor stability due to their dehydration properties over a long period, leading to their limited service-life in practical applications. To address this problem, we proposed a facile strategy to prepare a highly stable polyacrylamide (PAM)/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS)/MXene organohydrogel (PPMOH), in which ethylene glycol (Eg) is used as a bridge to enhance the interfacial bonding between the encapsulating layer and the PPMOH. On the other hand, LiCl was added to cooperate with the Eg to enhance the water retention ability of the organohydrogel, which exhibited excellent cycling stability (500 cycles) for as long as 90 days, and displayed good anti-freezing performance (−20 °C for 24 h). Moreover, MXene and PEDOT:PSS as well as the ions in the organohydrogel provided excellent sensitivity for the PPMOH, which demonstrated a high gauge factor of 4.71 and 10.69 in the range of 0–300% and 300–500%, respectively, as well as a fast response time of 100 ms. These multifunctional properties allow the prepared PPMOH to be used as a flexible strain sensor to detect both subtle and large deformation of human movements, which demonstrate great potential for use in human healthcare, intelligent robotics, and human–machine interface applications.