Research Project
6015208
Attempts to coat ultra-high molecular weight polyethylene (UHMWPE) prostheses with diamond and diamond-like carbon have failed to produce a practical solution, due to poor adherence and brittleness of diamond films. The main problem is that single layer coatings do not combine all of the required properties, such as good adhesion at the interface, no adhesion (interaction) at the surface, low internal stress and high hardness. The objective of this program is solve the wear problems associated with UHMWPE by coating at room-temperature with biocompatible, super- hard, tough, functionally graded nanocrystalline metalloceramic coatings. The proposed coatings would combine hardness, toughness, and low internal stress provided by multiphase nanostructures and superior adhesion provided by a gradual transition of chemical and mechanical properties through the film thickness. In preliminary investigations, we have deposited functionally graded Ti/TiN coatings onto UHMWPE with a hardness of 30 GPa. Pin-on-disk testing clearly demonstrates the protective ability of the coating, which shows no wear or delamination after 500,000 cycles in bovine solution, at a contact stress of 15 MPa. Uncoated UHMWPE, by contrast, shows significant wear. Phase I will optimize the fabrication of layer structures to produce excellent adhesion at the interface and no adherence at the surface (low friction) and demonstrate durability in bench-top testing. PROPOSED COMMERCIAL APPLICATIONS: There are over 500,000 knee and hip replacement surgeries performed each year in the United States. UHMWPE wear is a primary cause of device failure. A means of reducing UHMWPE wear, and consequently joint failure, has significant commercial potential.
