Yeh Hung-Chun, Yang Ruey-Jen, Luo Win-Jet
Department of Engineering Science, National Cheng Kung University, Tainan 701, Taiwan.
Phys Rev E Stat Nonlin Soft Matter Phys. 2011 May;83(5 Pt 2):056326. doi: 10.1103/PhysRevE.83.056326. Epub 2011 May 25.
In this paper, a series of numerical simulations was performed to investigate the pumping performance of electro-osmotic micropumps containing electrode arrays patterned on the upper and lower sides of a microchannel. The simulations have been analyzed with a linear electro-osmotic model based upon the Debye-Hückel theory of the double layer. The potential drop across the diffuse layer is assumed to be less than 25 mV (k(B)T/e), and there is a linear response between the surface charge and the voltage drop across the double layer. The double layer is not resolved but is lumped into effective parameters that are imported from the Debye-Hückel and Stern layers. We examined the effects of the relative positioning of the electrodes in the opposing arrays (i.e., symmetrical or staggered), and the phase lag and the angular frequency of the alternating current (ac) signals applied to the electrodes within the two arrays. A critical height of the microchannel was observed, below which the interactions of the applied electrical potentials on the walls became significant. The optimum pumping effect was obtained when the electrode arrays were symmetrical to one another around the centerline of the channel and were activated by ac potentials with a 0° phase shift. The corresponding angular frequency of the maximum pumping velocity for different phase shifts of the applied ac signals was also determined. Overall, the simulation results presented in this paper provide a useful insight into the optimal design parameters and operating conditions for micropumps containing two arrays of microelectrodes on the microchannel walls.
在本文中，进行了一系列数值模拟，以研究在微通道上下两侧图案化有电极阵列的电渗微泵的泵送性能。使用基于双层德拜-休克尔理论的线性电渗模型对模拟结果进行了分析。假定扩散层上的电位降小于25 mV（k(B)T/e），并且表面电荷与双层上的电压降之间存在线性响应。双层未作解析，而是集中为从德拜-休克尔层和斯特恩层引入的有效参数。我们研究了相对阵列中电极的相对位置（即对称或交错）以及施加到两个阵列内电极的交流（ac）信号的相位滞后和角频率的影响。观察到微通道的一个临界高度，低于该高度时，壁上施加电势的相互作用变得显著。当电极阵列围绕通道中心线彼此对称，并由具有0°相移的交流电势激活时，可获得最佳泵送效果。还确定了施加的交流信号不同相移下最大泵送速度对应的角频率。总体而言，本文给出的模拟结果为微通道壁上含有两个微电极阵列的微泵的最佳设计参数和操作条件提供了有益的见解。
