A stretchable and self-healing poly(vinyl alcohol)/polyacrylamide/polyaniline multi-network hydrogel for flexible strain sensors

In response to the development of electronic skin that mimics the functions of human skin, enormous efforts have been made to develop and synthesize new soft materials and to rationalize production techniques. Nevertheless, the development of electronically conductive materials that are elastic, stretchable and self-healing remains a major challenge. In this article, a series of self-healing, highly stretchable, solution-processable conductive polyaniline hydrogels with sequential hydrogen bonds are prepared by photopolymerization of acrylamide from a hydroxyl group located in the side chain of PVA, based on polyvinyl alcohol (PVA), acrylamide (AM), 2-acrylamide-2-methyl propane sulfonic acid (AMPS) and a polyaniline dispersion doped with phytic acid (PA). The conductive polyaniline hydrogel with an optimal composition can exhibit excellent self-healing capabilities and exceptional stretchability (up to 700 %). In the event of a tear, the mechanical properties can be restored with an efficiency of ≈ 90 % for 5 days without external stimulation, which is due to multiple hydrogen bonds and electrostatic interactions. In addition, this hydrogel, which has a gage factor (GF) of 2.73 and excellent levels of sensitivity, stability and repeatability, can be assembled into flexible sensors to capture dynamic human movements, such as joint flexion and vocalization. The conductive polyaniline hydrogel is produced through a process of photopolymerization and solution casting, which enables the production of electronic skin over large areas and at low cost.