基于三电层模型的交流电渗流速分析  

Alternating Current Electroosmosis Flow Rate Analysis Based on Electric-triple-layer Model

作　　者：李姗姗[1] 敖宏瑞[1] 侯珍秀[1] 姜洪源[1] 

机构地区：[1]哈尔滨工业大学机电工程学院,哈尔滨150001

出　　处：《机械工程学报》2011年第24期135-140,共6页Journal of Mechanical Engineering

基　　金：国家自然科学基金(51075087);流体传动与控制国家重点实验室(GZKF-201004)资助项目

摘　　要：微通道内交流电渗微泵的流速与电极表面双电层的结构与电荷分布密切相关,根据传统双电层理论和交流电渗速度公式可以预测交流电渗流速分布和速度峰值处的转折频率。试验发现,由此得出的交流电渗流速峰值比试验值大数倍。考虑紧密层和中间层厚度对交流电渗流的影响,提出三电层模型,给出三电层等效厚度和等效相对介电常数的求解方法,对传统的交流电渗速度公式进行修正,得出修正后的时间平均流速、位置平均流速和转折频率表达式。以宽度和间距均为20?m的平行电极阵列为试验对象,对其施加相位差90°的四相行波电场,用电荷耦合元件(Charge-coupled device,CCD)记录流场中荧光粒子的轨迹并用micro-PIV方法计算流场速度。设置不同的电层厚度参数对试验进行仿真。结果表明,紧密层厚度为几个溶剂分子大小(0.5 nm),而且中间层厚度为电极表面微观起伏高度(5 nm)时,仿真和试验结果非常接近,这表明三电层模型和修正后流速公式的有效性。ACEO（alternating current electroosmosis） flow rate is intimately associated with the structure and charge distribution of electric double layer（EDL）.Flow field distribution and cross-over frequency at which velocity reaches its peak can be predicted by classic EDL theory and flow rate formula.But the maximum velocity obtained theoretically is several times bigger than the experimental value.Considering the influences of Stern layer and middle layer thickness on ACEO flow rate,the ETL（electric-triple-layer） model is presented and effective thicknesses and relative permittivity of each layer are described herein,and then the formula for the description of time average and position average flow rate,as well as the cross frequency,are deduced.In the tests,a four-phase travelling wave electric field with 90° phase difference is applied to interdigitated electrode array with equal width and space of 20 μm to observe the trajectory of fluorescence micro particles by charge-coupled device camera,from which the flow rate is calculated based on the micro-PIV method.Different thicknesses of three layers were used in simulation.The experimental results show good agreement with simulation data when the thickness of Stern layer is with the size of several solvent molecules（0.5 nm） and middle layer thickness as the height of electrode surface micro topography roughness（5 nm）,which indicates the validity of the proposed ETL model and the modified velocity formula.

关 键 词：交流电渗 三电层 流速公式修正 电极表面粗糙度 

分 类 号：O361[理学—流体力学]