Boundary effect on electrophoresis:non-integrated/ eccentrically positioned colloidal particle
Date Issued
2008
Date
2008
Author(s)
Kuo, Chao-Chung
Abstract
The electrophoretic mobility of a colloidal particle near the boundary is investigated in this study for various types of problems by using finite element method. For the present study, we extend the integrated particle to non-integrated one like the toroid, and also consider the case a particle move along the axis of a long cylindrical pore eccentrically. The analysis include a toroid along the axis of a cylindrical pore, a finite cylinder eccentrically along the axis of a long cylindrical pore, a charge-regulated toroid normal to a large disk, and a soft toroid along the axis of a cylindrical pore. Another, about the charge model of both the particle and the boundary, we adapt the constant surface electric potential, constant volume charge density, and charge-regulated respectively. Referring to the skill of calculation, the coupled flow field and electric field equations or so-called electrokintic equations can be linearized assuming the applied electric field is weak and the surface potential is low, and therefore, a superposition is used to solve problem. We found that the particle mobility is affected by several factors, the charge conditions on the particle and the boundary, the geometric of the particle and the boundary, the size of the hole of the particle, the separation distance between the particle and the boundary, the eccentricity of the particle within the boundary, the double layer thickness, and the relative magnitude of the thickness of the charged membrane layer and its resistance. Results reveal that although the presence of the boundary has the effect of retarding the movement of a particle, it becomes advantageous if a toroid is sufficiently close to the boundary and cause a local minimum, especially for the case of hard toroid. For the case of the electrophoresis of a toroid normal to a large disk, the mobility may have a local maximum as the thickness of double layer varies. In addition, when a finite cylinder moves along the axis of a long cylindrical pore, generally speaking, the mobility of the particle increases with the increasing eccentricity, but for a short particle the mobility may have a local minimum as the eccentricity varies.
Subjects
Electrophoresis
Mobility
Boundary effect
Toroid
Soft particle
Eccentricity
Charge regulation
Type
thesis
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