Design, characterization, and performance evaluation of novel PVA / CS / CNF / MOP TN ionic conductive hydrogels for flexible sensors

Abstract Flexible hydrogel polymers with excellent stretchability, high conductivity, and biocompatibility are widely used to prepare flexible sensing devices. However, it remains difficult to simultaneously combine excellent tensile capacity and high ion conducting ability into a simple hydrogel material. While PVA‐based hydrogels have been developed before, this work focuses on a unique preparation method. It solves the engineering problem of making hydrogels that have both high elongation at break and high ionic conductivity. In the study, we introduced cellulose nanofibers (CNFs) into polyvinyl alcohol (PVA)/chitosan (CS) cross‐linked polymer networks to form triple network (TN) composite hydrogel. The labyrinthine three‐dimensional (3D) honeycomb through‐hole network nanostructure generated by the addition of CNF provides the hydrogel with excellent mechanical properties. Then, the simple salting‐out strategy of muriate of potash (MOP) solution gives the hydrogel superior mechanical properties and high ionic conductivity. The prepared PVA/CS/CNF/MOP TN ionic conductive hydrogel not only exhibits excellent mechanical properties (toughness up to 2.39 MJ m−3, fracture strength up to 1.78 MPa, fracture strain up to 350%) but also has impressive ionic conductivity (highest to 8.4 S m−1). The flexible hydrogel strain sensor assembled from the PVA/CS/CNF/MOP TN ionic conductive hydrogel showed remarkable sensitivity (gauge factor for 6.9) and the ability to detect human motions reliably. Besides, the hydrogel also has maintained long‐term antimicrobial and antioxidant properties. The study provided a new perspective on designing multifunctional materials featuring strong mechanical properties and high ionic conductivity, contributing to the advancement of flexible sensor technologies.