Cellulose Nanofiber and Sodium Caseinate Reinforced Polyacrylamide Ionic Conductive Hydrogel for Flexible Strain Sensors

Ionic conductive hydrogels attract significant attention in flexible electronics due to their excellent ion transport and mechanical flexibility, but limited elasticity and poor fatigue resistance hinder practical applications. In this work, a highly tough and mechanically stable hydrogel is fabricated by incorporating cellulose nanofibers (CNF) and sodium caseinate (SC) into a polyacrylamide (PAM) hydrogel matrix. CNF serves as a nanoscale reinforcing component that enhances the structural strength, while SC forms micellar structures that act as dynamic energy dissipation centers. The synergistic effect of CNF and SC significantly enhances the toughness and structural stability of the hydrogel. The resulting PAM/CNF/SC hydrogel exhibits a tensile strength of 0.71 MPa, a fracture strain of 1840%, and a high toughness of 3866.6 kJ m −3 . Benefiting from the presence of sodium ions in SC, the hydrogel sensor shows excellent ionic conductivity and a rapid response time of 195 ms, enabling sensitive detection of human motions such as joint bending, swallowing, and laryngeal vibrations. This work provides a simple and effective strategy for developing high-performance ionic hydrogels, offering strong potential for application in wearable and flexible electronic devices. Graphical This study presents a cellulose nanofiber- and caseinate-reinforced polyacrylamide ionic hydrogel with improved mechanical strength, toughness, and ionic conductivity. The hydrogel enables reliable and sensitive strain sensing, demonstrating strong potential for use in flexible wearable electronics.