Adhesive hydrogels have gained popularity in biomedical applications, however, traditional adhesive hydrogels often exhibit short-term adhesiveness, poor mechanical properties and lack of antibacterial ability. Here, a plant-inspired adhesive hydrogel has been developed based on Ag-Lignin nanoparticles (NPs)triggered dynamic redox catechol chemistry. Ag-Lignin NPs construct the dynamic catechol redox system, which creates long-lasting reductive-oxidative environment inner hydrogel networks. This redox system, generating catechol groups continuously, endows the hydrogel with long-term and repeatable adhesiveness. Furthermore, Ag-Lignin NPs generate free radicals and trigger self-gelation of the hydrogel under ambient environment. This hydrogel presents high toughness for the existence of covalent and non-covalent interaction in the hydrogel networks. The hydrogel also possesses good cell affinity and high antibacterial activity due to the catechol groups and bactericidal ability of Ag-Lignin NPs. This study proposes a strategy to design tough and adhesive hydrogels based on dynamic plant catechol chemistry.

Conductive hydrogels are promising materials for soft electronic devices. To satisfy the diverse requirement of bioelectronic devices, especially those for human–machine interfaces, hydrogels are required to be transparent, conductive, highly stretchable, and skin-adhesive. However, fabrication of a conductive-polymer-incorporated hydrogel with high performance is a challenge because of the hydrophobic nature of conductive polymers making processing difficult. Here, we report a transparent, conductive, stretchable, and self-adhesive hydrogel by in situ formation of polydopamine (PDA)-doped polypyrrole (PPy) nanofibrils in the polymer network. The in situ formed nanofibrils with good hydrophilicity were well-integrated with the hydrophilic polymer phase and interwoven into a nanomesh, which created a complete conductive path and allowed visible light to pass through for transparency. Catechol groups from the PDA–PPy nanofibrils imparted the hydrogel with self-adhesiveness. Reinforcement by the nanofibrils made the hydrogel tough and stretchable. The proposed simple and smart strategy of in situ formation of conductive nanofillers opens a new route to incorporate hydrophobic and undissolvable conductive polymers into hydrogels. The fabricated multifunctional hydrogel shows promise in a range of applications, such as transparent electronic skins, wound dressings, and bioelectrodes for see-through body-adhered signal detection.

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