Gravity assisted growth of self-organized anodic oxide nanotubes on titanium

The present work investigates the anodic growth of self-organized TiO2 nanotube arrays under different gravity fields. It is found that the aspect ratio of the nanotubes can be strongly affected by the orientation of the growing tubes within the natural gravity field or by high artificial gravitational fields in a centrifuge. Particularly remarkable is that under identical electrochemical growth conditions, the length of the nanotubes can be extended from 0.8 μm to 1.8 μm arranging the tube growth direction with or against the gravity field, or even extended up to 6.0 μm under high centrifugal forces (3220g).This strong effect is ascribed to gravity effects on the mass transport processes under diffusion controlled tube growth conditions.