Fresh or aged : Short time anodization of titanium to understand the influence of electrolyte aging on titania nanopores

Electrochemical anodization (EA) is a simple and cost-effective technique to fabricate controlled nanostructures on Ti substrates, such as TiO 2 nanotubes and nanopores. Electrolyte aging of organic EA electrolytes (repeated EA using non-target Ti before EA of target Ti) is recognized to influence the characteristics of the anodized nanostructures. However, there is limited information about how surface topography and electrolyte aging dictate the formation and characteristics of the anodized nanostructures. In the current study, short-time EA (starting at 10 s) of micro-machined Ti substrates was performed with electrolytes of various ages (fresh/unused, 15 h aged and 30 h aged), followed by evaluation of the TiO 2 nanopores (TNPs) characteristics in terms of topography, chemistry, stability and protein adhesion. The results showed that aligned TNPs were obtained earlier (120 s) with fresh electrolyte as compared to the aged electrolyte EA (600 s). Interestingly, TNPs fabricated using fresh electrolyte (at lower EA times) showed favorable wettability, protein adhesion capacity and mechanical properties compared with aged electrolyte counterparts. The findings of the study demonstrate how nanopore formation differs between fresh and aged electrolytes when performing EA of micro-machined Ti, which provides an improved understanding of electrolyte aging and its influence on anodized nanostructures.