Zhao Cunlu, Yang Chun
School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore, Republic of Singapore.
Phys Rev E Stat Nonlin Soft Matter Phys. 2009 Oct;80(4 Pt 2):046312. doi: 10.1103/PhysRevE.80.046312. Epub 2009 Oct 15.
Within the frame work of classic electromagnetic theory, a general electrical boundary condition describing the induced-charge electrokinetic phenomena at the liquid-dielectric interface is proposed in the present study. Two well-known limiting cases, i.e., perfectly insulating and perfectly polarizable wall boundary conditions, can be recovered from the present electrical boundary condition. By utilizing the proposed boundary condition, the induced-charge electro-osmosis (ICEO) flow in an infinitely long microchannel patterned with two symmetric polarizable dielectric blocks is investigated analytically. Fourier transform method is invoked to solve a biharmonic equation, which governs the (ICEO) flow field described by the stream function. Dimensionless parameters are introduced, and their effects on flow characteristics are analyzed. It is found that an increase in polarizability of the dielectric block enhances the slip velocity on its surface and thus induces a pair of counter-rotating vortices. Also, increasing the natural zeta potential on the upstream and downstream of the insulating microchannel walls leads to extinction of the vortex near the upstream insulating microchannel and suppression of the vortex near the downstream insulating microchannel.
在经典电磁理论框架内，本研究提出了一种描述液 - 电介质界面感应电荷电动现象的通用电边界条件。从该电边界条件可推导出两种著名的极限情况，即完全绝缘壁边界条件和完全可极化壁边界条件。利用所提出的边界条件，对由两个对称可极化介质块构成图案的无限长微通道中的感应电荷电渗流（ICEO）进行了理论研究。采用傅里叶变换方法求解双调和方程，该方程由流函数描述ICEO流场。引入无量纲参数，并分析其对流动特性的影响。研究发现，介质块极化率的增加会提高其表面的滑移速度，从而诱导出一对反向旋转的涡旋。此外，增加绝缘微通道壁上游和下游的自然zeta电位会导致上游绝缘微通道附近的涡旋消失，并抑制下游绝缘微通道附近的涡旋。
