In a recent study, published in the journal Nanotechnology, W Lee and J C Kim present a generic method for the preparation of highly ordered nanoporous anodic alumina with a pattern-addressed pore structure, in which the diameters of oxide nanopores are modulated with designated patterns.

The approach is based on pulse anodization of aluminum employing a series of potential waves that consist of two or more different pulses with designated periods and amplitudes, and provides a unique way of tailoring the internal pore structure of anodic alumina. Pores of the resulting AAO exhibit a high degree of directional coherency along the pore axes without any bifurcations (that is, branching of pores).

Anodic alumina membranes formed by the new pulse anodization method can be readily utilized as templates for developing novel nanowires or nanotubes, the diameters of which are modulated in controlled manners along their axes, and hence will enable not only the investigation of topography-induced various physical properties, but also could provide particle scaffolds for multiplexed bioassays.

The evolution of the internal pore structures of the pulse anodized sample was also investigated as function of pulse parameters. It was revealed that the effective electric field strength across the barrier oxide layer is a key controlling parameter governing the size of the pores and also the detailed geometry of the barrier layer. The study will shed light on the mechanism responsible for the self-organized growth of oxide nanopores during anodic oxidation of aluminum.

Additional information can be found in the journal Nanotechnology.