Enhancing\nTribo-Rehydration\nin Hydrogel by Brush-Like\nSurface and Its Modulation

Synovial\nexudation, creeping, and lubrication failure\nin natural\ncartilage under a long-term normal loading can be counteracted by\na tribo-rehydration (sliding-induced rehydration) phenomenon. Hydrogels,\nas porous materials, can also restore interfacial lubrication and\novercome creep through this strategy. At appropriate sliding velocities,\nwater molecules at the interface contact inlet are driven by hydrodynamic\npressures into the porous network to resist creep extrusion. In this\nwork, polyelectrolyte brushes were grafted onto the hydrogel surface\nto construct a loose, large-pore network structure and improve the\ninterface hydration, enhancing the tribo-rehydration. Compared to\nthe gel without grafted brushes, the grafted surface facilitated the\nwater molecules flowing into the gel network, and the hydrated brushes\neffectively anchor water at the interface and increase their enrichment\nat the contact surface for enhancing the rehydration. Finally, the\nstructure of the polymer brush was modulated by multivalent ions to\nexplore the relationship between the rehydration and structure. These\nresults indicate that constructing a loose, hydrated polymer brush\nlayer on the gel surface significantly enhances its tribo-rehydration\ncapability. This strategy can not only improve the load-bearing capacity\nand resistance to creep of the hydrogel but also effectively restore\nand maintain long-term lubrication.