Play‐Doh Inspired a Transformative, Shape‐Adaptive iHEÄLS Enabling Post‐Crosslinking Mechanical‐Biological Modulation and Its Effectiveness in Musculoskeletal Repair

Resorbable biomaterials are being developed as alternatives to traditional medical fillers for musculoskeletal repair. However, current materials fail to provide stable wound sealing and tissue regeneration due to inadequate conformal adaptability to irregular defects, weak adhesion in wet environments, and insufficient mechanical robustness balanced with biodegradability. Here, we present iHEÄLS, a transformative, shape‐adaptive biomaterial inspired by Play‐Doh, composed of cellulose nanocrystal (CNC)‐based triple‐networks. The interactions among the triple‐networks enable conformal defect filling, robust tissue adhesion, and shape stabilization through self‐healing. Mechanical training after crosslinking reinforces the network through aligned polymer chains and uniformly oriented CNC. As a biodegradable extracellular matrix, iHEÄLS promotes cell migration and osteogenic differentiation by leveraging nanomaterial incorporation and post‐crosslinking mechanical training to amplify bioactivity and mechanotransduction signaling. Additionally, iHEÄLS demonstrates enhanced hemostasis by quickly absorbing biofluids while maintaining malleability, facilitating effective mixing with autologous bone fragments, and promoting bone regeneration in a critical‐sized calvarial defect model. Overall, iHEÄLS integrates post‐crosslinking mechanical‐biological modulability with user‐friendly handling, providing a practical platform for musculoskeletal repair in emergencies.