Surface treatment of ultra-high molecular weight polyethylene (UHMWPE) by cold atmospheric plasma (CAP) for biocompatibility enhancement

Abstract

Ultra-high molecular weight polyethylene (UHMWPE) is one of the most commonly used polymers in joint replacements because of its biologically inert properties and low friction coefficient. However, it has downfalls relating to its wear, adhesion, and lubrication. In this study, UHMWPE samples were treated with a tubular helium cold atmospheric pressure (CAP) plasma source in order to improve three properties of the polymer: (1) its wear resistance, which was characterized by durometer hardness, (2) its lubrication characterized by water contact angle, and (3) its adhesion characterized by both root mean square surface roughness (Rq) and water contact angle. The polymer was treated by two different parts of the plasma plume (the base and the tip) at two different helium flow rates (1 L/min and 2.5 L/min), for different treatment times. Results of the plasma treatment showed a decrease in the contact angle of between 32 and 54 degrees, a significant increase in the roughness by up to 10 times the pristine surface, and no substantial change in the hardness. These improvements to the adhesion and lubrication properties of the polymer examined suggest that the treated surface could be more suitable for use in artificial joints.