Cartilage-inspired superlubricious hydrogels*

The uniquely-efficient lubrication of articular cartilage up to high physiological pressures in the major joints (hips and knees) has been attributed to surface boundary layers of macromolecules complexed with phosphatidylcholine (PC) lipids, where the exposed highly hydrated phosphocholine groups massively reduce friction via the hydration lubrication mechanism. We have emulated nature by constructing hydrogels exposing similar PC-based boundary layers at their surfaces, and by incorporating such PC lipids in the hydrogel bulk we achieve self-maintaining lubricant layers which permanently reduce the friction and wear of the hydrogels by up to a 100-fold or more, down to the superlubrication level (coefficient of friction < 0.01) at contact stresses up to many MPa. Such hydrogels hold promise in a wide range of biomedical applications.

(I thank my co-workers on this study: Weifeng Lin, Monika Kluzek, Noa Iuster, Eyal Shimony, Nir Kampf and particularly Ronit Goldberg)