Structural engineering of nanoporous anodic aluminium oxide by pulse anodization of aluminium


Nanoporous anodic aluminium oxide has traditionally been made in one of two ways: mild anodization or hard anodization. The first method produces self-ordered pore structures, but it is slow and only works for a narrow range of processing conditions; the second method, which is widely used in the aluminium industry, is faster, but it produces films with disordered pore structures. Here we report a novel approach termed “pulse anodization” that combines the advantages of the mild and hard anodization processes. By designing the pulse sequences it is possible to control both the composition and pore structure of the anodic aluminium oxide films while maintaining high throughput. We use pulse anodization to delaminate a single as-prepared anodic film into a stack of well-defined nanoporous alumina membrane sheets, and also to fabricate novel three-dimensional nanostructures.

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Figure 1: Pulse anodization.
Figure 2: Anodic aluminium oxide.
Figure 3: Modulation of pore diameter.
Figure 4: Delamination of AAO.


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We thank F. Müller for helpful discussions and comments on the manuscript. We also thank S. Hopfe for TEM sample preparation and K. Sklarek for SEM measurements. K.S. thanks the International Max Planck Research School for Science and Technology of Nanostructures for a scholarship. We acknowledge financial support from the German Research Foundation (STE 1127/8-1).

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Correspondence to Woo Lee.

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Lee, W., Schwirn, K., Steinhart, M. et al. Structural engineering of nanoporous anodic aluminium oxide by pulse anodization of aluminium. Nature Nanotech 3, 234–239 (2008).

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