Abstract
Microchannel whose one side wall consists of anode and the other side is cathode was fabricated for the particle manipulation such as separation and classification. Stainless steel, SUS304 and phosphor bronze copper, C5191P were employed as the electrodes. The upper and lower walls consist of glass or acrylic resin. The examined width and depth of the channel were 400 µm and 100 µm, respectively. The diameters of suspended monodisperse particles (Polymethyl methacrylate, 1,190 kg/m3) in ion-exchanged water are 1.8, 5, 10 µm, respectively. The particle behavior was recorded in a personal computer (PC) through microscope equipped with CCD module. When 2 volts were applied between the electrodes, larger particles with a surfactant moved to the cathode slowly while smaller particles always moved to anode. On the other hand, particles dispersed without surfactant always moved to anode regardless of the size. The particle migration led to concentration in the half side of the channel. It supposes that the former migration was caused by electro osmotic flow (EOF) near lower wall rather than by electrophoresis since particles appeared to be settled down and the vertical movement was observed near the edge of concentrated region. The EOF is generally utilized to convey the fluids in µ-TAS by applying high voltage (typically 1 - 10 kV) in the main stream direction. In the device newly developed, on the other hand, it seems that the extremely short distance between electrodes allowed the low voltage to cause the strong EOF. Further, it should be noted that the production of oxygen and hydrogen was not observed practically due to the low voltage. The feasibility as a new separator and classifier was shown by feeding suspensions into the channel. The many advantages of the device are described and the direction of further study is indicated.
