Highly ordered titania nanotube arrays with square, triangular, and sunflower structures

Focused ion beam guided anodization enables the fabrication of TiO2 nanotubes in a square arrangement with square cell shapes and in a graphite lattice arrangement with triangular cell shapes, which is impossible through self-organized anodization. TiO2 nanotubes in sunflower patterns are also obtained, which demonstrates the great potential of guided anodization in fabricating asymmetrical nanotubes.