Super-Stretchable Hydrogel Films with High Fracture Energy Enabled by Coordination Nanoparticles as Multifunctional Wound Dressings

Hydrogel films attract much attention as biomedical materials; however, they typically suffer from poor mechanical properties, which largely limit their practical applications. In this work, we show that coordination nanoparticles (CNs) can be used as high-functionality cross-linkers for the design of notch insensitive hydrogel films as multifunctional wound dressings. Fe-tannic acid CNs (FTCNs) with variable sizes and compositions are first synthesized, and the molecular assembly of FTCNs with polyvinyl alcohol results in strong and tough hydrogel films. Different from traditional fillers, FTCNs simultaneously increase the strength and toughness by combining the effect of particle reinforcement and dynamic chemical bonding. Appropriate selection of FTCNs enables a hydrogel film with an extension of more than 2300% and fracture energy as high as 3500 J/m 2 . Compared with the post-cross-linking of polyvinyl alcohol/tannic acid by Fe 3+, the more than 24-fold increase in fracture energy is attributed to the ability of FTCNs to maintain high elasticity and improve energy dissipation by locally concentrating ions. The nanocomposite hydrogel film is self-healable, recyclable, highly adhesive to the skin surface, antibacterial, and hemostatic, effectively promoting wound healing.