Surface Modification of Diamond-Like Carbon Film with Polymer Brushes Using a Bio-Inspired Catechol Anchor for Excellent Biological Lubrication

Diamond-like carbon (DLC) film has emerged as a promising material for biomedical applications, but its low tribological properties in air could not be adapted in water and biological fluids. Herein, mussel-inspired catechol adhesive is presented to functionalize DLC film and then polymer brushes are grafted by surface initiated atom transfer radical polymerization (SI-ATRP) to mimic excellent biological lubrication of articular cartilage. Macroscopic tribological evaluation demonstrates low and stable friction coefficient of polymer brushe modified DLC film in water and biological fluids when sliding with a soft polydimethylsiloxane (PDMS) hemisphere, owing to viscous fluid-like boundary lubricant film being formed by high hydration of polymer chains. The strong adhesive capability of catechol anchors also prevents polymer chains being sheared off from the substrate during friction tests. The friction responsiveness of PSPMA brushes is observed in electrolyte solution due to the conformation change of polymer chains. The successful functionalization of DLC with polymer brushes affords DLC film excellent biological lubrication and thus will broaden the scope of its applications in biomedical field.