Influence of surface heterogeneity on electrokinetically driven microfluidic mixing
Influence of surface heterogeneity on electrokinetically driven microfluidic mixing
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作者：
Erickson, D;Li, DQ
微流体系统中的电渗流仅限于低雷诺数状态。因此，电渗流系统中的物质混合本质上是扩散主导的，需要长的混合通道和保留时间来获得均匀的溶液。最近的研究表明，引入带相反电荷的表面不均匀性的微通道壁可以导致局部流动循环内的整体流动的区域。在这项研究中，我们试图调查这些流通区域，通过三维有限元数值模拟，然后使用它们作为一种方法，提高物种混合在T形微混合器。虽然所有表面异质性的情况都显示出增强混合效率，但是当异质区域的尺寸和异质性程度（即，非均相和均相zeta-电位之间的差）增加。在某些情况下，异质区域的存在下，所需的混合通道长度减少多达70%。
Electroosmotic flow in microfluidic systems is limited to the low Reynolds number regime. As a result species mixing in electroosmotic flow systems is inherently diffusion dominated, requiring both a long mixing channel and retention time to attain a homogeneous solution. Recent studies have shown that the introduction of oppositely charged surface heterogeneities to microchannel walls can result in regions of localized flow circulation within the bulk flow. In this study we seek to investigate these circulation regions, through 3D finite-element based numerical simulations, and then use them as a method of enhancing species mixing in a T-shaped micromixer. While all cases of surface heterogeneity are shown to enhance mixing efficiency, greater improvement is found when both the size of the heterogeneous region and the degree of heterogeneity (i.e., the difference between the heterogeneous and homogeneous zeta-potentials) are increased. In some cases the presence of heterogeneous regions is shown to reduce the required mixing channel length by as much as 70%.