Functionalization and Characterization of CP-Ti and Ti-6Al-4V Surfaces for Biomedical Implants

Titanium is used for biomedical implants due to its biocompatibility, corrosion and wear resistance, chemical inertness, and atoxicity; however, overtime, these implants fail likely due to corrosion, infection, wear and lack of osseointegration. Thus, surface modification of implant materials is required such that it improves aforementioned properties. In this study, titanium grade 2 (Ti-II) and grade 5 alloy (Ti-V) of various topographies were used. Goals of the study are to obtain, optimize and establish parameters for effective surface modification techniques with nano-scale accuracy. Sandblasted and acid etched Ti-II and Ti-V surfaces were modified using atomic layer deposition (ALD) technique to understand the substrates' surface wettability before and after ALD treatment, aging (i.e. over a period of 40 days with 5 days interval), and various cleaning methods (i.e., only N2 drying, DI-water wash, and methanol sonication). Several conclusions were obtained: 1) Ti-II and Ti-V surfaces become hydrophilic after TiO2 deposition using ALD compared to before ALD; 2) ALD treated hydrophilic Ti-II and Ti-V surfaces become hydrophobic after aging; and 3) aged hydrophobic Ti-II and Ti-V surfaces can be made hydrophilic by cleaning them with DI-water and methanol sonication. A study to investigate the change in TiO2 crystallinity of Ti-V samples was conducted by thermally oxidizing samples at 200 – 700 °C for 3 hours in air. Through Fourier transform infrared spectroscopy (FTIRS), it was found that thermally oxidizing Ti-V samples at ~ 400 °C provides mostly anatase TiO2 on Ti-V surface. Finally, a study addressing the change in surface wettability and composition of smooth, anodized-smooth, rough, and anodized-rough Ti-V substrates were investigated for (i) before and ii after thermal oxidation (TO) treatment and (ii) before and after aging. Our findings were: 1) before TO, anodized Ti-V surfaces show super-hydrophilic (water contact angle (WCA) of less than 5°) behavior, whereas, non-anodized Ti-V surfaces show hydrophobic behavior with WCA of 86 ± 7° and 57 ± 6°, respectively, 2) after TO at 450 °C, all samples become super-hydrophilic regardless of their wettability characteristics prior to TO, 3) 3 weeks after TO, the WCA of non- anodized samples increase, whereas, anodized samples WCA remain less than 10°, and 4) FTIRS shows that when samples are thermally oxidized at 450 °C, mostly anatase TiO2 is obtained.