Efficient hydrophilicity improvement of titanium surface by plasma jet in micro-hollow cathode discharge geometry

Surface hydrophilicity improvement of titanium (Ti) is of great significance for the applications of the important biomaterial. In this study, efficient hydrophilicity on the Ti surface is improved by an air plasma jet generated by a micro-hollow cathode discharge (MHCD) geometry. Elementary discharge aspects of the plasma jet and surface characteristics of the Ti surface are investigated by varying dissipated power (P_d). The results show that the plasma jet can operate in a pulsed mode or a continuous mode, depending on P_d. The plume length increases with P_d and air flow rate increasing. By optical emission spectroscopy, plasma parameters as a function of P_d are investigated. After plasma treatment, water contact angel (WCA) of the Ti sample decreases to a minimum value of 15° with P_d increasing. In addition, the surface topography, roughness, and content of chemical composition are investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), and x-ray photoelectron spectroscopy (XPS) with P_d increasing. The results show that Ti–O bond and O–H group on the Ti surface are beneficial to the improvement of the hydrophilicity of Ti surface.