Stretchable and tough PAANa/PEDOT:PSS/PVA conductive hydrogels for flexible strain sensors

Recently, flexible wearable health monitoring devices have significantly emerged as portable monitoring devices into human life. Owing to the applications of wearable electronics, flexible conductive hydrogel sensors that combine both stretchability and toughness have attracted lots of attention but still face challenges. Here, using semi-interpenetrating network (SIPN) strategy and cyclic freeze-thaw treatments, conductive hydrogels with stretchability, toughness, and sensitivity were prepared, which were composed of polyvinyl alcohol (PVA) as matrix network, poly (3, 4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) as conductive medium, sodium polyacrylate (PAANa) as reinforcing agent. The results showed that doping of PAANa not only improved the tensile strength, but also enhanced the electrical conductivity from 0.054 S m−1 to 0.146 S m−1. Furthermore, after being treated with saturated NaCl salt solution, the compact hydrogel exhibited an optimum tensile strength and electrical conductivity of 1.97 MPa and 0.327 S m−1, respectively. As an illustration, the obtained hydrogel was applied to detect finger and wrist bending movements, which exhibited stable amplitude and frequency. Given the enhanced mechanical and strain-sensitive properties of the wearable sensors, as well as the described propagable fabrication approach, this stretchable, tough hydrogel with sensitivity has potential applications in flexible wearable strain sensors.