Super-lubricating hydrogel enabled by microgel rolling and gradient porous structures

Hydrogels, with their tissue-like properties, biocompatibility, and soft properties, are potential biomimetic cartilage replacement materials. However, the conflict between their surface lubricity and load-bearing properties significantly limits their application. Here, we developed a structure-based hydrogel with super-lubricity and high load-bearing properties. Through ultraviolet (UV)-controlled dissociation, a gradient hydrogel surface was constructed. This structure effectively dissipates normal contact stress while maintaining a high surface hydration level, enhancing load-bearing capacity. Furthermore, micron-sized spherical gel particles were prepared using an emulsion method and incorporated into the highly hydrated polymer network, further enhancing the load-bearing capacity of the porous hydrogel and significantly reducing the coefficient of friction (COF) by converting sliding friction into rolling friction. Ultimately, through multiple synergistic effects, we achieved ultra-low friction performance, with a COF of approximately 0.0064 after 20,000 cycles under a 5 N load. This innovation provides an alternative solution for future biomimetic articular cartilage.