Control of the spatial distribution of porous alumina micro-domes formed during anodic oxidation

We found that micro-domes of porous alumina are self-assembled during anodic oxidation of an aluminum plate. We investigated the effects of the morphology of the initial aluminum surfaces on the formation of these micro-domes and found that the formation of micro-domes depends on the initial surface roughness of the substrate. We have also achieved spatial control over the distribution of these micro-domes through the use of artificial scratches on the initial surface. The origin of this control is the fact that micro-domes are preferentially formed inside hollow areas formed by the scratch. We investigated the inner structure of the micro-dome by separating it from the substrate. Inside the micro-domes, we observed nano-pore arrays similar to a porous alumina membrane, though the regularity of these pores is slightly worse than for the nano-pores around the micro-dome. These results indicate that the porous alumina micro-domes can be used as microscale nanoporous components.