Patterning hydroxyapatite biocoating by electrophoretic deposition

Patterned bioceramic coatings may find potential applications in orthopedic implants and biosensors. In this study, various hydroxyapatite (HA) patterns were created on silicon and titanium substrates. Electrophoretic deposition technique was used together with surface patterning of the cathode specimen. When gold/palladium patterns (hexagons, spherical dots, etc.) were created on the cathode surface, HA colloidal particles in ethanol would preferentially deposit on the gold-coated area and form patterns. When silicon, instead of gold, was evaporated onto a conducting cathode surface, HA mainly deposited on the exposed area of the substrate. Detailed mechanisms for forming HA patterns may involve local concentration of the electric field when a second metal is patterned on the cathode. The difference in electric field across the two metals on the cathode also enhances HA patterning through an electrohydrodynamic process. This study demonstrated the possibility and flexibility of electrophoretic deposition in patterning charged particles onto a substrate.