Articular cartilage inspired bilayer coating on Ti6Al4V alloy with low friction and high load-bearing properties

Articular cartilage possesses a unique biphasic structure that combines soft and hard substances to provide high load bearing and low friction across joints. Herein, a novel composite coating with a bilayer structure composed of a thin PTFE layer on top of a porous TiO₂ coating is fabricated on the Ti6Al4V alloy. The self-lubricating layer on top ensures low friction and the underlying TiO₂ layer provides the desirable wear resistance. With this soft/hard combination, the bio-inspired bilayer coating exhibits low friction (~0.1), ultrahigh load bearing (3.2 GPa), long low-friction lifetime, as well as superior wear resistance under dry sliding. The outstanding properties stem from regeneration (self-repair) in which PTFE is replenished continuously from the holes to the surface by frictional force to mend the scratched surface and counter abrasive wear. The findings reveal a new strategy to design smart biomimetic coatings with improved mechanical properties to expand the application of smart biomedical coatings to other areas.