Multiple Networked Cellulose Nanofiber/Sodium Alginate/Polyacrylamide Hydrogels Toughened by Interfacial Ionic Bond Engineering for Pressure Sensors

Wearable pressure sensors based on ionic conductive hydrogels have shown great potential in a variety of engineering fields, but their mechanical toughness is limited to practical applications. In this study, carboxylated cellulose nanofibers (CCNFs) were introduced into a dual-network hydrogel system made of sodium alginate (SA) and polyacrylamide (PAM) to prepare an ionic hydrogel sensor via an all-in-one integrated network strategy. The addition of CCNFs could provide new energy dissipation networks through the synergistic interactions of hydrogen bonds and ionic coordination bonds between CCNFs and polymer matrices. The multiple networked CCNF/SA/PAM hydrogels achieve an ultrahigh compressive strength of 13.3 MPa and a compressive toughness of 1312 kJ m –3 . Simultaneously, the pressure sensor based on the optimized hydrogel displays superior sensitivity (up to 64.2 kPa –1 ), broad working range (0.2–4.6 kPa), rapid responsiveness (80 ms), and excellent cycling stability, which can monitor a wide range of human movements and physiological activities.