Development of thin electrophoretically deposited hydroxyapatite layers on TiAl6V4 hip prosthesis

Hydroxyapatite ceramics for biomedical applications are often used in form of coatings to increase the biocompatibility of metallic implants, e.g. the femoral shaft of a hip prosthesis. A new method to produce such layers is electrophoretic deposition (EPD). The aim of this study was to investigate the influence of different powders and process parameters on the quality of the electrophoretically deposited thin HA layers. In order to attain layers with a thickness less than 50 urn, it is essential to use fine powders with particle sizes in the sub-micron range, and to stabilize these powders in suspension. We show that commercially available hydroxyapatite powders, which usually have a strong tendency to agglomerate, can be milled to particle sizes smaller than 500 nm by adding an organic dispersant. When such milled powders are used together with optimized process parameters, thin and homogenous layers can be produced by EPD. Using either aqueous or non-aqueous suspensions, hydroxyapatite layers can be deposited directly onto a metallic hip shaft, or onto a polymeric membrane, producing thin free-standing ceramics used for special biomedical applications.