Starch‐Phase‐Separation Enabling Soft‐Tough‐Interlocked Hydrogels for Effective Damage Tolerance and Sensing

ABSTRACT The pressing demand for advanced impact‐protective materials capable of reconciling high energy dissipation with tissue‐compliant flexibility remains challenging. Here, inspired by the osteochondral interface, a gradient starch‐based hydrogel with a continuous soft‐tough biphasic structure is fabricated via facile gravity sedimentation. Thermal initiation simultaneously triggers monomer polymerization and gelatinization‐retrogradation phase transitions in functionalized settled starch granules, enabling the integration of polyacrylamide chains into the crystalline modified starch framework. This process achieves an unprecedented 112.5‐fold difference in Young's modulus between the soft‐tough‐interlocked (STI) structure while maintaining interfacial integrity. The soft layer (matching human tissue modulus) ensures stretchability, while the tough layer withstands dynamic impacts up to 86.83 ± 1.66 MPa. Crucially, exceptional peak force attenuation (82%–90.6%) is demonstrated in falling‐ball tests. This is primarily attributed to the synergistic optimization of protective performance through a gradient dissipation mechanism that impact stress transmitted from the tough layer is dissipated over a larger surface area via deformation within the soft layer. The STI architecture further enables broad‐range mechanosensing (5 kPa–15.92 MPa) for real‐time impact energy monitoring. Furthermore, this hydrogel serves as both protective outer skin and shock‐absorbing, chemical‐resistant paws for robot dogs, demonstrating great potential for next‐generation robotics in harsh environments.