Titanium alloy is widely used as a biomaterial due to its superior biocompatibility, mechanical properties close to human bones, and enhanced corrosion resistance. These properties have made the alloys suitable for use in a wide spectrum of biomedical applications including artificial bones, artificial joints, dental roots, and medical devices. The excellent performance of titanium alloy is mainly due to the oxide film as shown in Figure 1 [1]. The functional composition of the oxide film is mainly titanium dioxide (TiO₂). Titanium dioxide has good biocompatibility, stable chemical property, and low solubility in water, which prevents substrate metal ions from dissolution. Furthermore, it also improves the wear and fatigue resistance of implants in the human body.