Electrically polarized micro-arc oxidized TiO2 coatings with enhanced surface hydrophilicity

Abstract The use of micro-arc oxidation titania (MAO TiO 2 ) coatings to modify titanium surfaces improves the biocompatibility of implant surfaces. To obtain hydrophilic MAO TiO 2 coating surfaces electric polarization, which induces surface electric fields in the materials and produces surface charges, was performed in this study. Electric polarization of the MAO TiO 2 coatings was confirmed by measuring the thermally stimulated depolarization current. After electric polarization treatment the MAO TiO 2 coatings did not exhibit any obvious changes in surface roughness, morphology, or phase components. X-ray photoelectron spectroscopy results indicated that electric polarization resulted in oxidation of the cathodic-faced surfaces and reduction of the anodic-faced surfaces. This result suggests that the existence of a concentration gradient of oxide ions/oxygen vacancies produced the stored space charge in the coatings. Reduction of the deionized water contact angle on the polarized MAO TiO 2 surfaces was maintained for longer periods compared with the non-polarized surface. Our study demonstrated that metastable electric fields across the MAO TiO 2 coating produced by electric polarization made it durably wettable by reducing the interfacial surface tension between the material and water.