Kim Sung Jae, Yoon Byung Jun
Department of Chemical Engineering, Pohang University of Science and Technology, Pohang 37673, South Korea.
Biomicrofluidics. 2019 Mar 8;13(2):024102. doi: 10.1063/1.5091936. eCollection 2019 Mar.
This work reported an analytic study of AC electroosmotic flows with a view to control the degree of mixing in a rectangular microchannel. Only with spatially non-uniform zeta potential distribution, fluid particles travel back and forth along a vortical flow field developed inside a microchannel. Although complex patterns of electroosmotic vortical flows can be obtained by various types of non-uniform zeta potential distributions, fluid particles always follow regular paths due to a laminar flow limit. To further facilitate the mixing of sample fluid, we propose a scheme that the zeta potential distribution was temporally non-uniform as well. General solutions for both the double layer potential distribution and the AC electroosmotic flow field are analytically determined by solving the unsteady Stokes equation with an electrostatic body force. As an illustrative example, we consider a case where two different types of non-uniform zeta potential distributions alternate with each other and the effects of both the AC frequency and the frequency of the alternation of the two zeta potential distributions on flow characteristics are examined using the Poincaré sections. Conclusively, one can either enhance or prevent mixing compared to a static electroosmotic flow, which is in line with previously demonstrated experimental works. Thus, the results presented would be an effective mean for controllable electroosmotic flow in a microfluidic platform.
这项工作报道了一项关于交流电渗流的分析研究，旨在控制矩形微通道内的混合程度。只有在空间不均匀的zeta电位分布情况下，流体颗粒才会沿着微通道内形成的涡旋流场来回移动。尽管通过各种类型的不均匀zeta电位分布可以获得复杂的电渗涡旋流模式，但由于层流限制，流体颗粒总是遵循规则路径。为了进一步促进样品流体的混合，我们提出了一种zeta电位分布在时间上也不均匀的方案。通过求解带有静电力的非定常斯托克斯方程，解析地确定了双层电位分布和交流电渗流场的一般解。作为一个示例，我们考虑两种不同类型的不均匀zeta电位分布相互交替的情况，并使用庞加莱截面研究交流频率和两种zeta电位分布交替频率对流动特性的影响。总之，与静态电渗流相比，可以增强或阻止混合，这与先前已证明的实验工作一致。因此，所呈现的结果将是微流体平台中可控电渗流的有效手段。
