Ring-Shaped Surface Microstructures for Improved Lubrication Performance of Joint Prostheses

Abstract

The microstructuring of surfaces is a highly researched field that is aimed at enhancing the tribological behavior of sliding surfaces such as artificial joints, which are subject to wear. Lubrication of the joint interface plays a key role in the wear process, although the mechanisms of lubrication are quite complex. In order to improve the lubrication, the surfaces of the articulating components can be modified by pulsed femtosecond-laser microstructuring. Through microstructuring, the apparent dynamic viscosity of the synovial fluid between the artificial joint can be increased due to its non-Newtonian properties. This may lead to better hydrodynamic lubrication and, therefore, reduced particle abrasion. Femtosecond laser-induced microstructures were investigated in a modified rheometer setup featuring a reduced gap size in order to reproduce and measure the interface between fluid and implant surface more accurately. As a test fluid, a synovial fluid substitute was used. The study has shown that an increase in the viscosity of the synovial fluid substitute can be achieved by microstructuring. Compared to a smooth implant surface, the apparent viscosity of the synovial fluid substitute increased by over 30% when ring-shaped microstructures of 100 µm diameter with an aspect ratio of 0.66 were implemented.

The Impact of Ultrashort Pulse Laser Structuring of Metals on In-Vitro Cell Adhesion of Keratinocytes

“…The laser-induced microstructures were characterized using a scanning electron microscope (SEM, EVO 15, Carl Zeiss Microscopy GmbH, Oberkochen, Germany) and a laser scanning microscope (VK-X200, Keyence, Osaka, Japan) [35] by measuring the dimple dimensions in their profile and determining the texture density (Table 1). Furthermore, after cleaning in an ultrasonic bath with deionized water and the subsequent drying of the surfaces, the structures were examined for their water contact angle in a wetting test rig of the type OCA11 (Dataphysics GmbH, Filderstadt, Germany).…”