Bulk-Aluminum Microfabrication for Micro Fuel Cells

We present a simple method for microfabricating microfluidic devices by wet etching of bulk aluminum wafers. Aluminum wafers are identical to silicon wafers in terms of dimensions and can easily be processed in standard clean room processes like lithography, etching, and thin film deposition. Aluminum thin film wet etching in phosphoric acid-based etchants is well established. In this paper, it is extended to much greater depths than before. 80 μm deep structures have been fabricated. A hydrogen-fueled micro fuel cell has been microfabricated from bulk aluminum. These fuel cells achieved very high current densities of 1.1 A cm^-2 and power density up to 228 mW cm^-2. Considering the simplicity of bulk aluminum micromachining, these results are very encouraging.