In Situ Grown Hydrogel Coatings With Robust Interfaces for Skinned Soft Devices

Robust hydrogel‐elastomer integration is crucial for soft electronics and robotics but hindered by interfacial fragility. Here, we present a spatially confined in situ photopolymerization strategy to grow hydrogel coatings directly from polydimethylsiloxane (PDMS). By confining the active radicals within the solvent‐swollen elastomeric boundary, this strategy achieves a bottom‐up growth. Crucially, both experimental characterizations and molecular dynamics (MD) simulations reveal a hydrogen‐bond‐mediated discrete nucleation process during the coating formation. This localized pre‐organization serves as physical evidence of the bottom‐up growth, which constructs a dual‐anchoring interface featuring simultaneous covalent grafting and topological entanglement. The dual‐anchoring (DA) hydrogel coatings achieve high interfacial toughness, long‐term stability, and applicability to other elastomers. We further extend this protocol for fabricating patterned conductive hydrogel coatings with high‐resolution reproduction of micron‐scale features. Furthermore, it enables rapid in situ fabrication of thin‐film actuators with enhanced actuation performance. This strategy presents a convenient protocol for integrating advanced hydrogel functionalities into soft matter systems.