Aluminum bulk micromachining through an anodic oxide mask by electrochemical etching in an acetic acid/perchloric acid solution

A well-defined microstructure with microchannels and a microchamber was fabricated on an aluminum plate by four steps of a new aluminum bulk micromachining process: anodizing, laser irradiation, electrochemical etching, and ultrasonication. An aluminum specimen was anodized in an oxalic acid solution to form a porous anodic oxide film. The anodized aluminum specimen was irradiated with a pulsed Nd-YAG laser to locally remove the anodic oxide film, and then the exposed aluminum substrate was selectively dissolved by electrochemical etching in an acetic acid/perchloric acid solution. The anodic oxide film showed good insulating properties as a resist mask during electrochemical etching in the solution. A hemicylindrical microgroove with thin free-standing anodic oxide on the groove was fabricated by electrochemical etching, and the groove showed a smooth surface with a calculated mean roughness of 0.2–0.3 μm. The free-standing oxides formed by electrochemical etching were easily removed from the specimen by ultrasonication in an ethanol solution. Microchannels 60 μm in diameter and 25 μm in depth connected to a microchamber were successfully fabricated on the aluminum

Fabrication of a meniscus microlens array made of anodic alumina by laser irradiation and electrochemical techniques

An anodic alumina microlens array was fabricated by laser irradiation and electrochemical techniques. An aluminum specimen covered with a porous oxide film was irradiated with a pulsed Nd-YAG laser, and then electropolished to dissolve the aluminum substrate. A well-defined semi-elliptical micropore was formed on the aluminum by electropolishing. The immersion of the electropolished specimen in a CrO3/H3PO4 solution resulted in the dissolution of the remaining anodic oxide film. Subsequent re-anodizing enabled the formation of a characteristic meniscus-shaped oxide film on the micropore. A microlens array made of the thin anodic alumina film, which showed flexibility and heat resistance, was successfully fabricated by the lift-off of the anodic oxide. (C) 2013 Elsevier Ltd. All rights reserved