Formation of super-hydrophilic surface of hydroxyapatite by ion implantation and plasma treatment

Control of the hydrophilic properties of hydroxyapatite Ca 10(PO 4) 6(OH) 2 (HAp) is important for the use of biocompatible materials. From this standing point, hydroxyapatite was implanted with N 2 +, O 2 + and Ar + with 1×10 17–1×10 21 ions m −2 at an energy of 20 keV. It was also immersed in an RF plasma of Ar, C 2H 5OH, CH 3OH and CF 4 induced at RF power of 50–150 W. Contact angles for various specimens were measured and the formation mechanism of hydrophilic surfaces are discussed. Hydrophilic HAp surfaces were formed by N 2 +, O 2 + and Ar + implantations and plasma treatments of Ar, C 2H 5OH and CH 3OH, with contact angles from 10° to 60°. Only the CF 4 plasma treatment can form super-hydrophilic surfaces with contact angles of 4–8°. The hydrophilic and super-hydrophilic formation mechanism was discussed based on analysis of XPS data.