Efficient Mixing or Liquid/Liquid-Extraction in Zigzag-Shaped Microchannel

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The Flow characteristics in a microchannel, operated by pressure-driven flow, are described by a low Reynolds-number flow : laminar flow. In laminar flow, the flow line runs parallel with the cannel-wall, so that the inertial effects on molecular motions and the turbulent mixing of solution do not occur. Owing to such flow characteristics, even when two solutions are introduced separately into a microchannel chip, the two folutions in the single channel can flow witout any mutual mixing. On the other hand, molecular diffusion along the channel-width direction take place, thus, solute molecules dissolved in one solution phase can cdistributed to the other phase : diffusional mixing, while the efficiency is insufficient. It is supposed that the flow characteristics might be influenced by the shape of the channel. In this study, therfore, shape effects of microchannel on a mixing of two miscible solutions and liquid/liquid extraction of two immiscible solutions were explored by usin spatially-resolved microspectroscopy. Polymer-substrate chips having a flat-side-walled channel (symmetrical and unsymmetrical zigzag side walled) were fabricated. In the unsymmetrical zigzag-side walled channel, the interface was sinusoidal reflecting on the shape, while it was flat in flat-or symmetrical-side-walled channel. Since the interface shape affects on contact time of the two solutions, the unsymmetrical zigzag-side walled channel syowed the most efficient mixing or extraction efficiency. In the symmetrical zigzag channel. the efficiency become worse than in flat-shape channel because of retention flow. These results were also supported fro, flow analysis by mathematical calculation.