Evaluation of the Antibacterial and Cell Culture Properties of Anodic Porous Alumina Prepared in Concentrated HSO.

The antibacterial activity of anodic porous alumina (APA) prepared using phosphoric, oxalic, and sulfuric acids was tested, and it was found that APA prepared using sulfuric acid had the highest antibacterial activity against and . In addition, the results of the antibacterial test using APA prepared with different concentrations of sulfuric acid showed that APA prepared in concentrated sulfuric acid exhibited significantly higher antibacterial activity. APA formed in concentrated sulfuric acid also showed excellent antibacterial activity even at a high culture medium concentration, at which bacterial cells tend to multiply easily.

Preparation of Ordered Nanohole Arrays by Two-Step Anodization of Austenitic Stainless Steel Substrates.

An anodic oxide film with a regular pore arrangement was formed by the two-step anodization of an austenitic stainless steel (JIS SUS304) substrate. In this study, we determined the anodization conditions under which the pore arrangement in the anodic oxide film became self-organized. After removing the anodic oxide film formed by the first anodization with a mixture containing CrO and HF, the residual substrate was anodized under the same conditions as those in the first anodization.

Antimicrobial Activity of Anodic Porous Alumina with Controlled Surface Structures.

The antimicrobial properties of anodic porous alumina (APA) formed by the anodization of Al substrates were evaluated. APA surfaces with needle-like projections fabricated under controlled preparation conditions exhibited high antibacterial activity against and . In antibacterial tests using APA with different interpore distances, all APA surfaces showed high antibacterial activity against , regardless of the interpore distance.

Preparation of Alumina Membrane Filters with Framework Structures by Al Anodization.

Alumina membrane filters consisting of a thin filter layer (200-700 nm in thickness) supported by a framework (30-100 μm in thickness) were fabricated on the basis of the anodization of an Al substrate. The solution permeability of alumina membrane filters with tubular pores of uniform size and shape varies with membrane thickness; therefore, membrane filters with a filter layer thickness of less than 1 μm showed high solution permeability. Although the filter layer is thin, it is reinforced by a thick framework, enabling the fabrication of large freestanding membrane filters (2.

Control of Water Droplet Transport Using Anodic Porous Alumina with a Wettability Gradient.

Water droplets can spontaneously move on surfaces with a wettability gradient, and such surfaces can be used in various functional devices. In this study, surfaces with a wettability gradient were prepared from anodic porous alumina with different pore arrangement regularities. The evaluation of the water droplet transport distance on the surfaces of the prepared samples showed that the pore arrangement regularity of the anodic porous alumina had no effect on the droplet transport distance.

Flat and roll-type translucent anodic porous alumina molds anodized in oxalic acid for UV nanoimprint lithography.

There is much interest in UV nanoimprinting as a fabrication method for various functional devices because of its suitability for efficient fine patterning. To form patterns on opaque substrates by UV nanoimprinting, it is essential to use molds through which UV light can pass. In this study, translucent anodic porous alumina (APA) molds for UV nanoimprinting were fabricated by the anodization of an Al substrate.

Effects of anodization conditions of stainless steel on the formation of ordered nanoporous structures with high aspect ratios.

The nanoporous structures obtained by the anodization of stainless steel are functional materials with various potential applications. It has been reported that nanoporous structures can be prepared by the anodization of stainless steel in an electrolyte containing fluoride ions. However, under the reported anodization conditions, the control range of the interpore distance of resulting nanoporous structures was narrow.

Preparation of size-controlled LiCoPO particles by membrane emulsification using anodic porous alumina and their application as cathode active materials for Li-ion secondary batteries.

Membrane emulsification using anodic porous alumina is an effective method for preparing monodisperse droplets with controlled sizes. In this study, membrane emulsification using anodic porous alumina was applied to the preparation of size-controlled particles composed of composite metal oxides. To obtain size-controlled composite metal oxide particles, membrane emulsification was performed using an aqueous solution containing a water-soluble monomer and metal salts as a dispersed phase.

Preparation of Polymer Nanopillar Arrays with Controlled Tip Shapes and Their Application to Hydrophobic and Oleophobic Surfaces.

Ordered arrays of nanopillars with controlled tip shapes were fabricated by a template formation process using anodic porous alumina with controlled pore shapes. Although various studies have been reported on the preparation of nanopillar arrays using anodic porous alumina as a template, there have been no reports on the formation of nanopillar arrays with precisely controlled tip shapes. Re-anodization of anodized samples in a neutral electrolyte can flatten the bottom of pores.

Preparation of Anodic Porous Alumina with Gradient Hole Size for Directional Droplet Transport.

A surface with a wettability gradient can be used as a surface where water droplets transport in one direction. In this report, a surface with a wettability gradient was formed by Al anodization and subsequent gradient etching. Since the surface wettability of anodic porous alumina formed by the Al anodization was dependent on hole size, anodic porous alumina with gradient hole size was prepared to form a surface with a wettability gradient.

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.

Flexible molds with micro-nano hierarchical structures on the surface were fabricated by a two-step template process using anodic porous alumina as a starting material. The obtained flexible molds could be used to form micro-nano hierarchical pillar arrays on the surface of glass tubes and convex lenses by photo-nanoimprinting. The contact angle characteristics of the surfaces with hierarchical pillar arrays were measured, and it was confirmed that they exhibit superhydrophobic properties with a water-droplet contact angle exceeding 150°.

Efficient fabrication of ordered alumina through-hole membranes using a TiO protective layer prepared by atomic layer deposition.

Ordered alumina through-hole membranes were obtained by a combination of the anodization of Al, formation of a TiO protective layer, and subsequent etching. Two-layered anodic porous alumina materials composed of TiO-coated and noncoated alumina were prepared by the combination of the anodization of Al and the formation of a TiO protective layer by atomic layer deposition (ALD). The obtained two layers of anodic porous alumina have different solubilities because the TiO thin layer formed by ALD acts as a protective layer that prevents the dissolution of the alumina layer during wet etching of the sample in an etchant.

Preparation of ordered nanohole array structures by anodization of prepatterned Cu, Zn, and Ni.

Anodic porous oxides with ordered nanohole array structures were prepared by the formation of concave arrays on the surface of Cu, Zn, and Ni substrates and the subsequent anodization of the prepatterned substrates. The concave arrays on the surface of the substrate were formed by Ar ion milling using an alumina mask. Although the anodization of Cu, Zn, and Ni substrates without prepatterning generates spongelike porous structures, ordered arrays of cylindrical nanoholes were obtained by the anodization of prepatterned substrates.

Renewable Superhydrophobic Surfaces Prepared by Nanoimprinting Using Anodic Porous Alumina Molds.

Renewable superhydrophobic surfaces based on laminated polymer films with nanopillar array structures were prepared. Polymer nanopillar arrays exhibiting superhydrophobic properties were prepared by nanoimprinting using anodic porous alumina as a mold. The hydrophobic properties of the obtained polymer nanopillar arrays could be controlled and optimized by changing the geometrical structures of anodic porous alumina molds used for nanoimprinting.

Preparation of Ordered Anodic Porous Alumina with Single-Nanometer-Order-Size Holes by Atomic Layer Deposition.

Ordered anodic porous alumina with controlled-size holes on the order of a single-nanometer scale was obtained by the atomic layer deposition (ALD) of AlO or TiO. The thin metal oxide layers of uniform thickness were formed successfully on the inner wall of the hole of the ordered anodic porous alumina with high aspect ratios by ALD. The hole diameter of the ordered anodic porous alumina could be controlled precisely by adjusting the number of cycles of ALD.

Self-ordered anodic porous alumina with inter-hole spacing over 1.5 μm.

Self-ordered anodic porous alumina with a long-range ordered hole arrangement having an inter-hole spacing of over 1.5 μm was prepared by anodization in a citric acid electrolyte containing a small amount of phosphoric acid. The inter-hole spacing of the ordered anodic porous alumina could be controlled within a range of 700 nm to 1.

Preparation of Ni micropillar arrays with high aspect ratios using anodic porous alumina template and their application to molds for imprinting.

Anodic porous alumina templates with controlled microscale geometrical structures were prepared by a process combining mask formation and subsequent selective etching of the alumina layer. In this process, the anisotropic etching of anodic porous alumina allows the preparation of anodic porous alumina with microhole array patterns having high aspect ratios. The electrodeposition of Ni using the obtained alumina templates generated an array of Ni micropillars with high aspect ratios.

SnO nanofibers prepared by wet spinning using an ordered porous alumina spinneret.

SnO nanofibers with uniform diameters were obtained by wet spinning using ordered anodic porous alumina as a spinneret, followed by heat treatment. Ordered alumina through-hole membrane is a suitable spinneret material for nanofiber spinning owing to its nanohole array structure with uniform-sizes holes. A polymer solution containing a Sn salt was used as a precursor solution for the wet spinning.

Fabrication of ideally ordered TiO through-hole membranes by two-layer anodization.

Ideally ordered TiO through-hole membranes were obtained by a combination of Ti substrate pre-patterning and two-layer anodization. The Ti substrate was pre-patterned by Ar ion milling using ideally ordered porous alumina as an etching mask. Each concave pit formed by dry etching acted as an initiation site for hole development during anodization, and ideally ordered anodic porous TiO was produced by anodization using an electrolyte containing fluoride ions.

Control of thermal radiation in metal hole array structures formed by anisotropic anodic etching of Al.

An efficient preparation process for Al hole array structures emitting wavelength-selective thermal radiation that is based on the anisotropic anodic etching of Al was demonstrated. The formation of an ordered hole array was achieved by a masking process prior to the anodic etching. The present process allows the preparation of large samples because the masking of the Al foil has a high throughput owing to the simple printing process using a flexible stamp.

Selective through-holing of anodic porous alumina membranes with large area.

Anodic porous alumina membranes with site controlled through-holes were prepared by the formation of a masking layer on the surface of anodic porous alumina and subsequent selective second anodization in concentrated sulfuric acid to form a readily soluble layer. After the anodization, the residual Al substrate was removed, and the highly soluble alumina layer formed in concentrated sulfuric acid was dissolved selectively by wet etching. An advantageous point of this process is the controllability of the pattern of through-holes, and the preparation of large samples with selective through-holes is possible.

Correction: Preparation of superhydrophobic surfaces with micro/nano alumina molds.

[This corrects the article DOI: 10.1039/C8RA07497F.].

Preparation of superhydrophobic surfaces with micro/nano alumina molds.

Polymer micro/nano hierarchical structures were successfully formed by photo-nanoimprinting using anodic porous alumina molds. Anodic porous alumina molds with hierarchical structures were prepared by the anodization of an Al substrate with a micro-concave array. The obtained surfaces with hierarchical structures exhibited superhydrophobicity.

Preparation of nanoporous alumina hollow spheres with a highly ordered hole arrangement.

Nanoporous alumina spheres with an ordered hole arrangement were prepared through a two-step anodization of small Al particles. The hole periodicity in the ordered anodic porous alumina could be controlled by adjusting the anodizing conditions. Nanoporous hollow spheres were also obtained by removal of residual Al in an etchant.

Fabrication of monodisperse polymer nanoparticles by membrane emulsification using ordered anodic porous alumina.

Uniformly sized droplets of photocurable monomer were obtained through membrane emulsification using highly ordered anodic porous alumina as a membrane. Subsequent polymerization of the monomer generated polymer particles, whose sizes could be controlled by changing the size of the pores in anodic porous alumina. The size distribution was very narrow owing to the uniformity of pore size in the anodic porous alumina used for the emulsification.