Hydrophobic associations and cellulose nanofibers reinforced PVA/PAM multi-network conductive hydrogel with high sensitivity, fast response, and excellent mechanical properties

Abstract

With the growing demand for green and biocompatible flexible sensors, hydrogels have drawn attention as a new material for flexible wearable devices. However, it remains a challenge to develop hydrogel flexible sensors with excellent mechanical properties, high toughness, high sensitivity and fast response through a simple approach. In this work, hydrophobic associations and cellulose nanofibers were introduced into a polyacrylamide/polyvinyl alcohol (PAM/PVA) dual-network hydrogel. The incorporation of a hydrophobic system strengthens the first polymer network, while cellulose nanofibers (CNF) enhance the second PVA freeze-thaw network. Notably, CNF tightly bridges the dual networks, forming extensive hydrogen bonds with the reinforced double-network structure. Under the synergistic effects of multiple networks and hydrogen bonding interactions, the composite hydrogel exhibits superior mechanical performance (1.82 MPa), outstanding toughness (5.41 MJ/m³), excellent fatigue resistance, and good recovery properties. Additionally, the composite hydrogel demonstrates superior electrical conductivity, high sensitivity (GF = 7.89), and stable electrical signal output. It performs exceptionally well in practical applications, such as monitoring motion at human joints and integrating with peripheral circuits to control robotic hands. In summary, this work presents a simple and cost-effective method for fabricating high-performance composite hydrogels, which show great potential in tissue engineering, flexible electronics, and human-computer interaction.