Robust Super-Lubricity for Novel Cartilage Prototype Inspired by Scallion Leaf Architecture

The simultaneous achievement -under physiologically high contact pressuresof ultra-low friction, nearly zero surface wear, and long lifetime in the development of human cartilage prosthetics is still a big challenge. In this work, inspired by the unique lubrication mechanism of scallion leaves resulting from the synergy of oriented surface micro-topography and mucus hydration, a novel layered soft hydrogel as cartilage prototype is developed by chemically embedding thick hydrophilic polyelectrolyte brush chains into the sub-surface of a high strength anisotropic hydrogel bulk. It exhibits an anisotropic polymer network with unique mechanical properties (tensile strength: 8.3 to 23.7 MPa; elastic modulus 20.0 to 30.0 MPa), anisotropic hydrated surface texture, super-lubricity, and excellent wear resistance. Thydrogel architecture can exhibit low coefficient of friction (COF) less than ≈0.01 under a wide range of contact stresses (0.2 to 2.4 MPa) and maintain cartilage-like long-lasting (50k sliding cycles) robust super-lubricity (COF ≈ 0.006) and nearly-zero wear under high contact pressure (≈2.4 MPa) condition. Theoretical underpinning reveals how multiscale surface anisotropy, mechanics, and hydration regulate super-low friction generation. This work provides a novel design paradigm for the fabrication of robust soft materials with extraordinary lubricity as implantable prototypes and coatings.