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

Abstract

implants, e.g., blood contacting implants such as heart valves and stents, load bearing joints and ophthalmic surgery. [1][2][3] However, many in vitro experiments on biocompatibility and tribology showed contradictory results, due to different experimental setup and different fl uids used as lubricants. [4][5][6][7] The low tribological properties of DLC in air or vacuum could not be adapted to load bearing joints operated in biological fl uids, which would be one of the major restrictions on its application for coating material of biological implants where lubrication is of great importance. Fortunately, surface functionalization of DLC fi lms is a practicable and effective method to solve the key problems. However, there were few reports on surface functionalization of DLC fi lms to give DLC required biological properties. Hamers and Garrido used photochemical process to generate a monolayer of amine groups on nanocrystalline diamond surfaces and then DNA or proteins was covalently attached, leading to stable biologically active surfaces. [ 8,9 ] In this paper, mussel inspired catechol and following polymer brushes would be presented to functionalize DLC fi lm to meet its aqueous lubrication.Generally, water is not a good lubricant for the friction system of some inorganic materials because it is very hard to form stable boundary fi lm due to low viscosity. However, the extremely low friction properties supported by water lubrication were found in some biological surfaces, for example, the vitreous body of eyes, the organs of human body and synovial joints, such as hip, knee and fi nger joints. [ 10 ] The effi ciency is attributed to the complex structure of self-adaptive cartilage [ 11 ] combined with synergetic effects of self-assembled structure of biological additives (such as phospholipids, hyaluronan (HA), lubricins) and bottle-brushes-like glycoproteins. The biomolecules in synovial fl uid can immobilize onto surfaces of cartilage and combine large amounts of water molecules to aid lubrication. [12][13][14][15] For instance, HA-aggrecans complexes showed much better boundary lubrication properties than the HA alone, because of the fl uid hydration sheaths strongly bound to the highly charged segments on the aggrecans. [ 16 ] Over the last decades, some artifi cial methods have been employed to mimic the excellent bio-lubrication. Water-soluble polymers [ 17 ] and polymer brushes grafted from fl at surfaces [ 18 ] are two effective approaches to reduce friction in aqueous medium. HA, a linear Diamond-like carbon (DLC) fi lm has emerged as a promising material for biomedical applications, but its low tribological properties in air could not be adapted in water and biological fl uids. Herein, mussel-inspired catechol adhesive is presented to functionalize DLC fi lm 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 c...

A Robust Lubrication System Using an Ionic Liquid Polymer Brush

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Salt-Responsive Zwitterionic Polymer Brushes with Tunable Friction and Antifouling Properties

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The Tethered Fibrillar Hydrogels Brushes for Underwater Antifouling

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