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

压力驱动流作用下微通道内的流动特性可用一种低雷诺数流动：层流来描述。在层流中，流线与管壁平行，因此不会对分子运动产生惯性影响，也不会发生溶液的湍流混合。由于这种流动特性，即使将两种溶液分别引入到微通道芯片中，单通道中的两种溶液也可以流动而不发生任何相互混合。另一方面，分子沿通道宽度方向发生扩散，溶解在一种溶液相中的溶质分子可以分布到另一种溶液相中：扩散混合，但效率不高。假定流道形状对流动特性有一定的影响。因此，本研究利用空间分辨显微光谱分析技术，研究了微通道的形状对两种互溶溶液的混合和两种非互溶溶液的液/液萃取的影响。制备了具有扁平侧壁通道(对称和非对称之字形侧壁)的聚合物基板芯片。在非对称之字形侧壁通道中，界面在形状上呈正弦反射，而在平坦或对称侧壁通道中，界面呈平坦状。由于界面形状对两种溶液的接触时间有影响，非对称的锯齿形壁面通道具有最高的混合效率或萃取效率。在对称的之字形水道中。由于滞留流动的存在，效率变得比平板流道差。这些结果也为数学计算的流动分析提供了支持。

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.