Preferential Interfacial Engineering of Hydrogels via Interdigitated Nanoparticle Assembly

Hydrogels have emerged as promising materials across various fields, including biomedical, electronic, and robotic applications, due to their intrinsic softness and biocompatibility. Despite these advantages, the development of hydrogel‐based functional materials and devices remains limited by the narrow range of materials that can be seamlessly and robustly integrated with water‐swollen hydrogel matrices. This interfacial incompatibility significantly restricts their functional expansion and practical applicability. Herein, we present a strategy for the facile integration of hydrogel with a broad spectrum of materials, including polymers, metals, and biological tissues, by employing interdigitated metal nanoparticle (NP) assembly to form nanobridges on hydrogel surfaces. This approach is based on ligand‐exchange‐assisted NP assembly, which induces strong affinity between metal NPs and the hydrogel matrix. The partially exposed NP domains act as nanobridges that mediate chemical or physical bonding with functional or even hydrophobic components. Notably, this approach enables effective use of commercial bonding agents onto hydrogel, regarded previously as incompatible with hydrogels, thereby extending their applicability as adhesives for biological tissues. This work establishes a broadly applicable platform for constructing a variety of hydrogel‐based systems with versatile interfacial compatibility.