Single wedge sliding tests to investigate the mechanism of UHMWPE particle generation with microfabricated surface textures

Microfabricated surface textures have been applied to generate narrowly distributed UHMWPE wear particles with different sizes and shapes. The purpose is to study the effects of UHMWPE induced bioactivity that leads to the failure of total joint implants. Our previous study has developed the principles of surface-texture design to control the particle size and shape. The objective of this paper is to investigate the UHMWPE particle-generation mechanism with the surface textures containing wedge-shaped cutting edges. Single tip sliding experiments have been designed to investigate the kinematics and the material response of the UHMWPE particle-generation process. With constant penetration depth setup, strain hardening of UHWMPE under a wedge-tip sliding process has been quantified. With constant normal load conditions, we are able to simulate the wedge feature sliding over UHMWPE material with a scaled-up wedge tip. From in situ observation of the process, the kinematics of the sliding process of the wedge tip has been elucidated. The shear stress-induced molecular orientation and embrittlement of the material further contribute to the fracture of UHMWPE and formation of the wear particles. Overall, these results provide experimental evidence of the UHMWPE particle generation mechanism with microfabricated surface textures. The basic science behind the generation of UHMWPE particles by surface-texture design has been further illustrated.