突扩管流中微米颗粒分离效率的研究

助欧拉和拉格朗日方法数值模拟了突扩微尺度管道流中微米颗粒的分离情况. 在采用有限体积法求解电荷密度场、电场和流场的基础上，通过基于改进的Langevin方程研究了微管道中不同位置处的微米颗粒在水动力和介电电泳力综合作用下的运动轨迹. 研究发现:电渗流的驱动能力随着扩张比(ER)的增加而提高，然而其提高的趋势逐渐变小；当微米颗粒仅在水动力作用下时，随着ER的增加，颗粒之间的有效分离距离(ESL)随之线性增加，此时ESL与ER的比值约为5.9; 若是考虑介电电泳力对于微米颗粒运动的影响, ESL与ER的比值下降为4.79, 由此可以看出介电电泳力对突扩微管道流中的微米颗粒的分离效果有着一定的负面影响. 上述结论对于基于介电电泳技术设计的生物粒子分离芯片的优化设计有很大价值. 

SEPARATION EFFICIENCY OF MICROPARTICLE IN THE DIVERGENT ELECTROKINETIC MICROCHANNEL FLOW

This study reports a numerical simulation ofseparation efficiency of microparticles in the divergent microchannel flowusing the Eulerian and Lagrangian methods. The flow field, ion field andelectric field are simulated numerically with finite volume method first,then microparticles are injected from the inlet of the microchannel andtracked with the Langevin-equation-based model, in which dielectrophoreticforce is included. It has been found that the microchannel's pumpingcapability increases with the increase of divergent ratio (ER). In addition,the effective separation length between microparticles increases linearlywith the increase of ER. With and without consideration of Dielectrophoresis(DEP), the ration of ESL to ER is 5.9 and 4.79, respectively. Itmeans that thenegative DC-DEP always reduces the separation efficiency in the divergentmicrochannel. The aforementioned conclusion is helpful for the designoptimization of separation apparatus.