Surface Texture Design to Generate Specific Sizes and Shapes of UHMWPE Wear Particles

Osteolysis induced by UHMWPE wear particles has emerged as the critical failure mechanism of artificial joints. However, the detailed mechanism of osteolysis and bone resoprtion induced by wear particles leading to the loosening of the total joint replacement is still not clear. To investigate the effects of size and shape of particles on biological response, particles with controlled size and shape are needed. The paper describes a novel technique where controlled size and shape of UHMWPE wear particles can be generated through rubbing against a textured surface. The basic principles of surface texturing to generate different size and shape of wear particles through rubbing have been developed. The surface features are fabricated through conventional semiconductor microfabrication techniques. Various designs were attempted and the results suggested that micro-cutting mechanisms of a visco-elastic material are complex but can be controlled through three dimensional surface features. Specific length of UHMWPE particles can be generated by controlling the cutting-edge length of a surface wedge. The particle width can be controlled by the cutting-edge height, normal load, and the sliding speed. With appropriate surface-texture design, UHMWPE particles can be generated with desired sizes and shapes.