Huang Kuan-Da, Yang Ruey-Jen
Department of Engineering Science, National Cheng Kung University, Tainan, Taiwan.
Electrophoresis. 2006 May;27(10):1957-66. doi: 10.1002/elps.200500721.
In electrokinetically driven microfluidic systems, the driving voltage applied during operation tends to induce a Joule heating effect in the buffer solution. This heat source alters the solution's characteristics and changes both the electrical potential field and the velocity field during the transport process. This study performs a series of numerical simulations to investigate the Joule heating effect and analyzes its influence on the electrokinetic focusing performance. The results indicate that the Joule heating effect causes the diffusion coefficient of the sample to increase, the potential distribution to change, and the flow velocity field to adopt a nonuniform profile. These variations are particularly pronounced under tighter focusing conditions and at higher applied electrical intensities. In numerical investigations, it is found that the focused bandwidth broadens because thermal diffusion effect is enhanced by Joule heating. The variation in the potential distribution induces a nonuniform flow field and causes the focused bandwidth to tighten and broaden alternately as a result of the convex and concave velocity flow profiles, respectively. The present results confirm that the Joule heating effect exerts a considerable influence on the electrokinetic focusing ratio.
在电动驱动的微流体系统中，运行期间施加的驱动电压往往会在缓冲溶液中诱发焦耳热效应。这种热源会改变溶液的特性，并在传输过程中改变电势场和速度场。本研究进行了一系列数值模拟，以研究焦耳热效应，并分析其对电动聚焦性能的影响。结果表明，焦耳热效应会导致样品的扩散系数增加、电势分布改变，并且流速场呈现出不均匀的分布。这些变化在更紧密的聚焦条件下和更高的外加电场强度下尤为明显。在数值研究中发现，由于焦耳热增强了热扩散效应，聚焦带宽会变宽。电势分布的变化会诱发不均匀的流场，并分别由于凸形和凹形速度流剖面导致聚焦带宽交替变窄和变宽。目前的结果证实，焦耳热效应会对电动聚焦比产生相当大的影响。
