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Title: | 帶電邊界與極化效應對膠體粒子電泳行為的影響 Effects of a charged boundary and polarization on the electrophoresis of a colloidal particle |
Authors: | Zheng-Syun Chen 陳政勛 |
Advisor: | 徐治平(Jyh-Ping Hsu) |
Keyword: | 電泳,電泳度,邊界效應,極化效應,電滲透流,軟球,電荷可調節, Electrophoresis,Mobility, Boundary effect,Double-layer polarization,Electroosmotic flow,Soft particle,Charge-regulated condition, |
Publication Year : | 2008 |
Degree: | 博士 |
Abstract: | 本論文是以有限元素法探討不同幾何系統中邊界效應與電雙層極化對膠體粒子電泳行為的影響。我們的分析將文獻中關於低表面電位的限制延伸至任意電位。所考慮的幾何系統包含單顆硬球或軟球沿一長圓管軸心的泳動、單顆圓柱形粒子沿一長圓管軸心的泳動、單顆球形粒子在球形孔洞中任意位置的泳動、以及單顆橢球形粒子在球形孔洞中心的泳動。在軟球粒子的問題中,我們特別分析了其外層薄膜物性以及電荷可調整模式對其泳動行為的影響。我們假設相較於由粒子或邊界所建立的電場,外加電場較弱,故原來相互耦合的電場、流場及離子濃度場方程式可以線性化,並以疊加原理求解。
數值模擬的結果顯示,下列因素對膠體粒子的電泳度有顯著的影響:粒子與邊界的表面帶電情況、粒子與邊界的幾何形狀、粒子與邊界的距離、電雙層厚度、粒子表面電位。此外,軟球粒子的泳動行為會受到其薄膜層之物性所影響。帶電邊界對膠體粒子泳動有重要影響,因為它除了會有效增加或減少粒子的電泳速度外,在某些條件下,甚至會導致膠體粒子泳動方向的改變或電泳速度產生一局部極值。本論文所獲結果提供了電泳設計與操作具參考價值的資訊。 The electrophoretic behavior of a colloidal particle near a charged boundary is investigated theoretically for various types of geometry. These include a rigid or soft sphere along the axis of a cylindrical pore, a finite cylinder along the axis of a cylindrical pore, a sphere at an arbitrary position in a spherical cavity, and an ellipsoid at the center of a spherical cavity. The governing equations and the associated boundary conditions are solved numerically based on a finite element method. Based on the assumption that the applied electric is weak relative to that established by the particle and/or the boundary, two key effects are considered, namely, electroosmotic flow and double-layer polarization. The results of numerical simulation reveal that the electrophoretic mobility of a particle is mainly affected by several factors: the charged conditions on the particle and the boundary, the geometry of the particle and the boundary, the separation distance between the particle and the boundary, the thickness of double layer, and the level of the surface potential. For the case of a soft particle, the mobility is also influenced by the nature of its membrane layer. We show that the presence of an electroosmotic flow and the effect of double-layer polarization are capable on influencing both quantitatively and qualitatively the mobility of a particle. For instance, the mobility of a particle can change its sign and/or have a local extreme as the thickness of double layer varies. These proved valuable information for the design and implementation of an electrophoresis operation. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/37524 |
Fulltext Rights: | 有償授權 |
Appears in Collections: | 化學工程學系 |
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ntu-97-1.pdf Restricted Access | 9.28 MB | Adobe PDF |
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