考虑双电层内离子空间效应的行波交流电渗流计算模型研究  

Study on the Calculation Model for Travelling-wave Electroosmotic(TWEO) Flow by Considering Steric Effect of Finite-sized Ions in Double Layers

作　　者：朱晓璐[1] 杨逸飞[1] Zhu Xiaolu;Yang Yifei(School of Mechanical and Electrical Engineering,Hohai University,Changzhou 213022,China)

机构地区：[1]河海大学机电工程学院,江苏常州213022

出　　处：《科技通报》2017年第2期4-8,共5页Bulletin of Science and Technology

基　　金：江苏省自然科学基金(批准号:BK20161197);常州市科技计划(社会发展)项目(批准号:CE20165029);中央高校基本科研业务费专项资金项目(批准号:2015B04414)资助的课题

摘　　要：行波交流电渗流是微流体芯片中一种重要的流体驱动方式,但目前其常规理论的预测值仍与实验值有较大差异,甚至有时出现流向相反的情况。本文提出了一种用于估算行波电渗流速随频率和溶液电导率而变化的数学模型(包括反向电渗流)。在该模型中,通过综合考虑双电层内离子的空间立体效应和在双电层溶剂分子电粘阻滞效应,推导了双电层内的有效粘度。另外,模型中引入参数Kc和Kr用于校正双电层的等效电容和电阻,并进行了拟合计算。结果表明,在双电层内的粘度大于溶液粘度的十倍乃至百倍以上,双电层特征系数值在高频段的减小导致电极表面电渗作用的分布改变,从而使流动反向。实验结果与模型计算结果相近,论证了本模型较好的预测效果。Travelling–wave electroosmosis (TWEO) is an important driving mode in microfluidic devices.However, there is still obvious discrepancy between the simulative EO flow rates and the experimental values, and sometimes the flow direction in experment was opposite to that in simulations. Here, we propose an approximate mathematical model to estimate the variation in TWEO flow velocity (including flow reversal) with respect to frequency and electrolyte conductivity. In the model, an effective viscosity inside electrical double layer (EDL) and two characteristic coefficients of EDL are proposed and mathematically derived. The simualtion results show the viscosity inside EDL is at least more than 10 times larger than that in bulk solution and it coincides with the flow decay with ascending electrolyte conductivity in experiments. The decrease of characteristic coefficients of EDL at high frequecies leads to distribution alterations of electroosmostic effect, thus resulting in flow reversal. Simulation data are in accordance with those in experiments, which demonstrates the ability of this model to quantitatively predict TWEO flow.

关 键 词：电渗 反向流动 双电层 离子空间立体效应 有效动力粘度 

分 类 号：O335[理学—一般力学与力学基础]