Supramolecular lignin-containing hydrogel for flexible strain sensor via host-guest interaction and dynamic redox system

A supramolecular lignin-containing hydrogel was constructed via host-guest interaction and dynamic redox system. The dynamic redox reaction between Ag+ and polyethylene glycol-lignosulfonate (PEG-LGS) could trigger free radical polymerization. The host-guest interaction between α-cyclodextrin and PEG-LGS could effectively enhance the adhesiveness and mechanical properties. The hydrogel exhibited a typical three dimensional structure with uniformly distributed silver nanoparticles. It exhibited an elongation at break of 1390%, a fracture stress of 171 kPa. The hydrogel displayed strong adhesiveness towards various surfaces that the adhesion strength of the hydrogel to aluminum reached as high as 48 kPa. The hydrogel displayed great conductivity as high as 2.71 S/m and good self-healing behavior. The hydrogel could be applied as strain sensor and pressure sensor. Most importantly, this hydrogel sensor exhibited high sensitivity over a wide strain range with the GF values of 3.06, 5.92, and 10.38 in the strain ranges of 0–80%, 80%–240%, and 240%–1000%, respectively.