Preparation of Ideally Ordered Anodic Porous Alumina by Prepatterning Process Using a Flexible Mold

Abstract

Ideally ordered anodic porous alumina with controlled interpore distances was formed by fabricating a resist mask using a flexible mold and subsequent anodization. Prior to forming the resist pattern on the surface of an Al substrate, Al was pre-anodized at 10 V to prepare the fine porous structure, which acts as a resist adhesive layer. After the formation of the resist mask using a flexible mold, an arranged array of cavities with Al exposed at the bottom was formed by the selective dissolution of the oxide layer at resist openings. The subsequent anodization of the sample with the cavity array generated ideally ordered anodic porous alumina because alumina holes were formed at the bottom of cavities during anodization. This process allows the preparation of ideally ordered anodic porous alumina even on a curved Al surface owing to the flexibility of the mold. In addition, this process can also be applied to the preparation of an ideally ordered anodic porous alumina with a large sample area because the Al substrate can be patterned without high pressure. The obtained sample can be used for various applications requiring an ideally ordered hole array structure.

Fabrication of Ideally Ordered Anodic Porous Alumina on Glass Substrates by Stamping Process Using Flexible Stamps

“…In our previous report, we showed that the stamping process using PDMS stamps could be used to form ordered anodic porous alumina on the curved surfaces of cylindrical Al substrates. 31 Here, we show the results of applying this process to an Al substrate with a convex lens shape. For cylindrical Al substrates, wrapping the PDMS stamp around a curved surface allows the stamp surface to come in contact with the curved sample surface.…”

“…After sputtering, the samples were heat-treated in a vacuum furnace at 150 °C-450 °C for 7 h. Then, an anodic porous alumina thin film that serves as a mask layer was formed by anodization in 0.3 M oxalic acid at 16 °C for 30 min under a constant voltage of 10 V. In our previous report, we showed that forming a resist mask directly on the Al surface results in a pattern with many defects due to polymer reflow during the heat treatment to remove the toluene completely. 31 On the other hand, if a porous alumina layer is formed on the Al surface in advance, pattern deformation during heat treatment can be prevented due to the anchoring effect of the porous surface structure. It has also been found that the smaller the pore size of the pre-formed porous alumina layer, the higher the pattern transfer accuracy.…”

“…In our recent study, we showed a stamping process using flexible stamps made of polydimethylsiloxane (PDMS) as a new method to control the starting point of pore generation in anodic porous alumina. 31 This process is suitable for the formation of large-area ordered anodic porous alumina, because resist masks that control the starting point of pore generation can be formed on Al substrates by pressing the flexible stamp with a finger. In other words, large-area patterning, which conventionally requires high pressure with hard molds, can be achieved at a low pressure using flexible stamps.…”

Micro-nano hierarchical pillar array structures prepared on curved surfaces by nanoimprinting using flexible molds from anodic porous alumina and their application to superhydrophobic surfaces

“…First, anodic porous alumina with hierarchical structures was prepared by an integrated process composed of anodization and selective patterning. 27,28 Next, polymer negatives of anodic porous alumina with the hierarchical structures were formed, and nally, the exible mold was obtained by molding using the polymer negative as a mold. This process can effectively form high-aspect-ratio micropillars with nanopillar arrays at their tips on curved surfaces.…”

High-Performance pH Sensor Electrodes Based on a Hexagonal Pt Nanoparticle Array-Coated Nanoporous Alumina Membrane

“…Researchers and scientists are interested in ordered porous structures because they have many fascinating characteristics [ 1 , 2 , 3 ]. The surface porosity, particularly the order surface, has a high surface that increases the interaction between the active sites and the electrolyte [ 4 , 5 ].…”