Highly Stretchable, Sensitive, and Durable Ag/Tannic Acid@Graphene Oxide-Composite Hydrogel for Wearable Strain Sensors

Flexible and wearable strain sensors have received extensive attention in the preparation of human–machine interface equipment, intelligent robots, and personalized health-monitoring biosensors. However, it has been a formidable challenge to develop materials with satisfying stretchability, sharp and quick sensitivity, and good linearity. Herein, we report a multifunctional nanocomposite hydrogel with outstanding stretchability, fatigue resistance, and electrical conductivity by adding Ag nanoparticle-coated graphene oxide (Ag/TA@GO)-based nanocomplexes into a polyacrylamide (PAM) hydrogel matrix. This Ag/TA@GO-PAM nanocomposite hydrogel shows an ultrahigh stretchability of 1250% and excellent conductivity (0.15 S·m–1). The sensitivity is improved to GF = 3.1; meanwhile, the preeminent linear sensing property is achieved in the ultrawide strain range of 0 to 1000%, with a high R2 value of 0.994. Moreover, when the Ag/TA@GO-PAM hydrogel is assembled into a wearable strain sensor with a sandwiched structure, it can detect large and delicate motions (for example, facial expression and pronunciation), with excellent sensitivity and durability. In addition, the nanocomposite hydrogel is further explored from practical aspects for circuit assembly and repair, E-skin of bionic robots, and information encryption. Therefore, this study provides a basis for multifunctional wearable nanocomposite hydrogel sensors.