Boundary‐Lubricated Hydrogels with Load‐Bearing Capacity via Microphase Separation Strategy

Abstract Lubricating hydrogels show promise as cartilage substitutes but face mechanical fragility (elastic modulus <100 kPa) and fluid‐dependent lubrication failure under physiological loads. hydrogels are presented with nanoconfined water via microphase‐separated structures, combining hydrogen‐bond‐stabilized polymer‐dense domains and hydrated regions. By tuning hydrated nanopore size (≈10 nm) and enhancing bound water content, these hydrogels achieve boundary lubrication with ultralow friction (coefficient of friction, COF≈0.01) under extreme conditions: contact pressures >10 MPa, velocities spanning 1–100 mm s ⁻¹ . Additionally, hydrogels demonstrate effective lubrication under sub‐zero temperatures. The hydrogen bond‐reinforced network balances exceptional mechanical properties—compression modulus of 53.8 MPa and fracture energy of 54462.6 J m ^{− 2} —surpassing conventional hydrogels. Their uniform heterogeneous structure enables self‐renewal post‐wear, sustaining long‐term lubrication. This design decouples mechanical robustness from lubrication sustainability, overcoming the traditional interdependency where mechanical degradation accelerates lubrication failure. By optimizing polymer network topology to regulate water states, load‐bearing boundary lubrication is enabled, addressing critical limitations in cartilage‐mimetic materials. The strategy offers a pathway for durable hydrogels in biomedical applications requiring simultaneous pressure resistance, velocity adaptability, and environmental resilience.