Polyacrylamide-Chitosan based magnetic hydrogels with high stiffness and ultra-toughness

Magnetic hydrogels have potential applications in various fields such as soft actuators and drug delivery since they could be controlled remotely and responded promptly. However, magnetic hydrogels are generally brittle, which greatly limits their applications. It remains a challenge to synthesize magnetic hydrogels with high toughness, large stretchability, and outstanding magnetic properties. In this study, we fabricated a type of Fe3O4/CS-PAAm conductive magnetic hydrogels with ultra-high toughness. Microscopically, the gels were strengthened by ionic cross-linking, molecular entanglement, hydrogen bonding between nanoparticles and the polymeric networks. The magnetic hydrogels could generate a dramatic amount of heat under an alternating magnetic field, suggesting potential applications in tissue heating and drug releasing. Additionally, the deformations of the gels could be easily tuned by magnetic fields, allowing the gels to function as soft magnetic response actuators. Moreover, the gels had outstanding conductivity and strain sensitivity, making them good candidates as flexible electronic sensors.