Osmophoresis of a Spherical Vesicle in Small Pore
Date Issued
2005
Date
2005
Author(s)
Hsu, Yun-Shuan
DOI
en-US
Abstract
Osmophoresis is the motion of vesicles in liquid solution in response to an applied solute concentration gradient. The presence of a neighboring boundary causes two basic effects on the osmophoretic velocity of a vesicle: first, the local concentration gradients on the vesicle surface are altered by the wall, thereby speeding up or slowing down the vesicle; secondly, the wall enhances the viscous interaction effect on the moving vesicle. In this dissertation, the boundary effects on the osmophoresis of a spherical vesicle in small pores are studied theoretically in the quasi-steady limit of negligible Reynolds and Peclet numbers.
First, in chapter 2, we analyze the osmophoretic motion of a spherical vesicle along the centerline of a circular cylindrical pore. The imposed solute concentration gradient is uniform and parallel to the pore wall, which may be either impermeable to the solute molecules or prescribed with the far-field concentration distribution. To solve the equations of conservation of mass and momentum, the general solutions are constructed from the fundamental solutions in both cylindrical and spherical coordinates. The boundary conditions are enforced first at the pore wall by the Fourier transforms and then on the vesicle surface by a collocation technique. Numerical results for the osmophoretic velocity of the vesicle relative to that under identical conditions in an unbounded solution are presented for various values of the relevant properties of the vesicle as well as the relative separation distance between the vesicle and the pore wall.
In chapter 3, we investigate the osmophoretic motion of a spherical vesicle situated at an arbitrary position between two infinite parallel plane walls. The imposed solute concentration gradient is uniform and perpendicular to the plane walls. To solve the equations of conservation of mass and momentum, the general solutions are constructed from the superposition of the fundamental solutions in both cylindrical and spherical coordinates. The boundary conditions are enforced first at the plane walls by the Hankel transform and then on the vesicle surface by a collocation technique. Numerical results for the osmophoretic velocity of the vesicle relative to that under identical conditions in an unbounded solution are presented for various values of the relevant properties of the vesicle-solution system as well as the relative separation distances between the vesicle and the plane walls.
The collocation results of both of the cases discussed in chapters 2 and 3 agree well with the approximate analytical solutions obtained by using a method of reflections. The presence of the neighboring boundaries enhances the vesicle velocity, but its dependence on the relative vesicle-wall separation distances is not necessarily to be monotonic. In general, the boundary effect on osmophoresis is quite significant.
Subjects
滲透泳
osmophoresis
Type
thesis
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