Synergy of phospholipid and hyaluronan based super-lubricated hydrogels

Synthetic hydrogels have been widely studied for the application of artificial joints and other biomedicals. In this work, the synergy of phospholipid and hyaluronan (HA) based super-lubricated hydrogel was synthesized with zwitterionic polymers through free-radical polymerization. The coefficient of friction could reduce down to 0.004, reaching a super-lubricated state, which exhibited a remarkable reduction of friction (approximately 85%) in comparison to that of the original hydrogel in the absence of lipids and HA. The friction reduction was observed under a wide range of sliding velocities, normal loads, and different upper friction materials (including steel, glass, polytetrafluoroethylene, and silicon nitride). The enhanced lubrication performance was mainly attributed to the formation of a robust lipid-based hydration boundary layer at the hydrogel interface with the synergistic lubrication effect between lipids and HA arising from electrostatic interaction. Our approach may provide the potential application for cartilage replacement and artificial joints and help us develop hydrogels with good lubrication characteristics.