Characteristics of microfilters made of anodic oxide films of aluminium

Various types of micro-filters were made of anodic oxide films of aluminium by dissolving substrate and barrier layer partially in the form of a circle. The diameter of the micro-pores in the filters were controlled by bath voltage during anodizing and by pore-widening technique. The flow rate of distilled water through the films was measured under Various conditions and revealed that the measured values of flow rate of water relatively agreed with the values calculated by the equation of Hagen;Poiseuille. It was also demonstrated by experiments of breakdown of the filter by air-pressure that the strength of the filter was nearly proportional to the thickness of the filter and was inversely proportional to diameter of filter, as suggested by the equation from material strength theory.