微通道中电渗流及微混合的离子浓度效应

Effects of Ion Concentration on Electroosmotic Flow and Micromixing in Microchannels

电渗流广泛应用于微流控芯片中的流体输运与混合.该文提出了一种离子浓度梯度对电渗流及微混合产生影响的变量模型,采用有限元分析方法对微通道中电渗流及微混合的离子浓度效应进行了数值模拟,分别讨论了zeta电势、介电常数等对微通道内流场和浓度场的影响规律,定量分析了微混合效率.结果表明,当zeta电势和介电常数随浓度变化时,微通道中流场分布不均匀,离子分布不对称.当溶液浓度趋近1 mol/L时,溶液基本无法进入微通道.微混合效率随溶液间浓度差的增大而减小,而且浓度差越大越能在较短距离内到达充分混合.

Electroosmotic flow is widely used to transport and mix fluids in microfiuidic chips. A variable model for the ion concentration gradient effects on the electroosmotic flow and mi- cromixing in microchanneis was presented. The effects were investigated numerically with the finite element method. The impacts of the zeta potential and the dielectric constant on the flow field and concentration field were also analyzed. The micromixing efficiency in the microchannel was evaluated quantitatively. The results show that the flow field is inhomogeneous, and the distribution of the ion concentration will be asymmetric in the microchannel while the zeta po- tential and the dielectric constant vary with the ion concentration. When the concentration of the electrolyte solution is approximate to 1 mol/L, the solution essentially couldn＇ t be driven into the microchannel. The micromixing efficiency decreases with the ion concentration differ- ence between the electrolyte solutions, and the larger the difference is, the shorter the distance is needed to reach perfect mixing.