Boundary Effects on the Electrophoresis of a Porous Particle
Date Issued
2010
Date
2010
Author(s)
Cheng, Wen-Li
Abstract
Electrophoresis of a porous particle normal to a well conducting plane and along the centerline of a cylindrical pore are investigated theoretically in this study. Due to the particular physical configurations, the systems were characterized by bipolar and sphere coordinates respectively. The coupled electrical potential, ion conservation and hydrodynamic equations, or the so-called electrokinetic equations, are linearized by assuming the applied external electric field is weak. A pseudo-spectral method based on Chebyshev polynomials and Newton-Raphson iteration scheme are adopted to solve the resulting electrokinetic equations numerically.
We find that the polarization effect and the counterion condensation are more apparent as the fixed charge density of the porous particle increases. The presence of the solid boundary retards the particle motion in general, and is more significant when the electric double layer surrounding the particle is thick. The degree of polarization effect and counterion condensation would vary due to the deformation of electric double layer. Moreover, for the case of a charged pore, an electric double layer will occur near the pore surface, and an electroosmotic flow will take place upon the external electric field. The flow can either enhance the particle motion or deter it, depending on the potential sign on the pore. The direction of particle motion may even change when the pore is highly charged.
Subjects
electrophoresis
porous particle
bipolar coordinate
polarization
counterion condensation
electric double layer
boundary effect
electroosmotic flow
Type
thesis
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