軟球粒子垂直於平板之電泳現象

Electrophoretic Behavior of a Soft Particle Normal to a Plane

鄭文立(Wen-Li Cheng)

指導教授 ： 李克強

國立臺灣大學/工學院/化學工程學研究所/碩士(2006年)

https://doi.org/10.6342/NTU.2006.03053

摘要

本論文主要是以假性光譜法對軟球粒子垂直於一不帶電平板的電泳現象進行數值模擬。軟球粒子因擁有特殊的物理結構，因此能夠更貼切地描述生物粒子或人造複合粒子，也會造成許多不同於硬球的結果出現。為了適當描述此系統，我們同時使用球座標以及雙球座標進行兩區聯解的運算，並在弱外加電場的假設下，將部分相互耦合的電場、流場及離子濃度場方程式線性化，再利用牛頓-拉福生疊代法求得系統之穩態解。

研究結果發現，當軟球層摩擦係數愈大，其感受到的流體拖曳力愈大，電泳速度隨之下降，反之當摩擦係數愈小時，則其愈接近硬球膠體粒子的結果。而在軟球層中加入固定電荷後，會對平衡系統產生較大的影響，能提供額外的電力使電泳速度上升。此外，發現平板的邊界效應在電雙層厚度很大或是軟球粒子愈靠近的時候相對明顯，在電雙層厚度很小時則無顯著的變化。

關鍵字

電泳現象 ； 軟球 ； 雙球座標 ； 電雙層 ； 邊界效應

並列摘要

The electrophoretic behavior of a soft particle normal to a plane is investigated in this study using pseudo-spectral method. Due to its unique physical structure, soft particle system can be used to model some bio-particles or artificial particles appropriately. We treat the problem by separating the physical region into two domains useing spherical coordinates and bispherical coordinates respectively. The coupled hydrodynamic, electrical potential and ion conservation equations or the so-called electrokinetic equations are then linearized assuming the applied electric field is weak. The resulted problem is solved numerically using Newton-Raphson iteration scheme.

We find that as the friction coefficient of the soft particle increases, the drag force increases as a result, thus the electrophoretic motion becomes slow. If the friction coefficient is very small, the result will be very similar to the typical colloid particle. When we introduce the fix charge density, the equilibrium state is affected greatly and generate extra electric force which enhance the electrophoretic motion. Moreover, we find that the boundary effect is more significant when the thickness of electric double layer is large or the soft particle is closer to the plane.

並列關鍵字

electrophoretic behavior ； soft particle ； bispherical coordinates ； electric double layer ； boundary effect

參考文獻

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