Coaxial anodic oxidation under dynamic electrolyte conditions for inner surface patterning of high-aspect-ratio and slim Ti tubes

Abstract

We report a feasible and facile approach of coaxial anodic oxidation under dynamic electrolyte conditions for patterning Ti tubes. Uniform TiO2 nanotube arrays are prepared at the inner surface of Ti tubes with 930mm in length and 3mm in diameter, being the largest aspect ratio ever reported. Interestingly, a resulting structure of nanowire bundles standing upright the nanotubes, anodized at 20V for 4h with an electrolyte flow rate of 12.2μL/s, exhibits superhydrophobic feature with a water contact angle of 165° and sliding angle of <2°. Its potential application in drag reduction is also demonstrated.