Adhesive Ion-Conducting Hydrogel Strain Sensor with High Sensitivity, Long-Term Stability, and Extreme Temperature Tolerance

Ion-conducting hydrogels with excellent flexibility and ductility have great potential in human movements monitoring. However, some obstacles, including a small detection range, low sensitivity, low electrical conductivity, and poor stability under extreme conditions, impede their use as sensors. Herein, an ion-conducting hydrogel comprising acrylamide (AM), lauryl methacrylate (LMA), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and a water/glycerol binary solvent (named the AM-LMA-AMPS-LiCl (water/glycerol) hydrogel) is designed, which exhibits an enlarged detection range of 0%-1823% and improved transparency. Notably, the ion channel constructed using AMPS and LiCl significantly improves the sensitivity (gauge factor = 22.15 ± 2.86) of the hydrogel. The water/glycerol binary solvent endows the hydrogel with electrical and mechanical stability under extreme conditions (70 and -80 °C). Furthermore, the AM-LMA-AMPS-LiCl (water/glycerol) hydrogel exhibits antifatigue properties for 10 cycles (0%-1000%) because of noncovalent interactions such as hydrophobic interactions and hydrogen bonding. The hydrogel can be used to monitor human movements such as joint bending and perceive subtle discrepancies such as different joint bending speeds and angles, showing its great potential application in human movement monitoring, electronic skin, and wearable devices.