Robust Superlubricity in Artificial Cartilage Hydrogels via Gradient Stress Dissipation and Comb‐Like Polymer Structures

Abstract Hydrogels are among the most promising materials for joint cartilage replacement due to their hydrophilicity, high water content, biocompatibility, and lubricating properties. Despite extensive research on these hydrogels, achieving biomimetic materials with high load‐bearing capacity, low friction, extraordinary lubrication, and wear resistance remains challenging. Inspired by the distinctive structure of articular cartilage, an artificial cartilage hydrogel (ACH) is developed that parallels natural articular cartilage in structure, mechanism, and performance. The material features porous surface structures, similar to porous soft surface of articular cartilage, which effectively reduce friction under load‐bearing conditions. Additionally, superhydrophilic molecules, resembling the structure of aggrecan on cartilage surfaces, grow within these porous structures. They enable the surface to bind water molecules firmly, significantly improving its load‐bearing and elastic properties. From the surface to the middle to the deep layer, cross‐linking density increases gradually, similar to the distribution of collagen fibers in articular cartilage to provide subsurface contact stress attenuation. The hydrogel designed with this strategy exhibits high load‐bearing capacity and an ultra‐low coefficient of friction (COF≈0.0028 at 20 N for 36 000 cycles) and maintains stable super lubricity under varying loads. This design approach for hydrogel materials offers a novel strategy for developing biomimetic cartilage replacement materials.