Preparation and Bioactivity of Micro-Nano Structure on Ti6Al4V Surface

Titanium (Ti) and its alloys have been widely used in the medical field for dental and orthopedic surgeries owing to their excellent mechanical and biological properties. However, much effort has been devoted to the surface modification on Ti-based implants for better biological response in medical applications. Bioactive layers with micro- and nano-scale structures and morphologies can increase the specific surface area of the implants and facilitate rapid osseointegration, which has shown good biological behaviors both in the laboratory and clinical setting. Sandblasting and acid-etching (SLA) technology has become one of the most commonly used surface modification processes for currently marketed dental implants, since it can be easily operated and is efficient. However, studies on etching behavior are still limited. In this study, concentrated hydrochloric acid ((36%-38%)HCl, mass fraction) and mixed diluted acid (20%HCl : 30%H2SO4 = 1 : 1, volume fraction) were used to etch Ti6Al4V, and an ultrasonic field was applied to the acid etching treatment. The influence of different etching parameters on the surface structure and morphology of Ti6Al4V was discussed, including the acid etching reagent, acid etching time, and ultrasonic field. Moreover, through the combination of SLA and induction heating treatment (IHT) oxidation, the micro- and nano-scale hierarchical structure was prepared on the surface of Ti6Al4V. The evolution of surface topography, chemistry, roughness, wettability, and bioactivity of the hierarchical structure was discussed. The micro-scale composite pores combing dozens of micron pores and several micron pores were obtained by SLA. Within a certain etching time range, with the prolonging of the etching time, the step structure on the inner wall of the micro-pores becomes more obvious, and ultrasound can accelerate the acid etching. After the IHT at 800 degrees C, the micro- and nano-scale hierarchical surface with micro-scale composite pores and nanoscale oxide was obtained. Compared with the SLA surface, there was a decrease in surface roughness and an increase in wettability. Furthermore, after soaking in simulated body fluid (SBF) for 14 d, a homogeneous hydroxyapatite (HA) layer was formed on the micro- and nano-scale structured Ti6Al4V surface, suggesting high biological activity of the fabricated structure.