多孔球粒子之振盪電泳行為與介電泳現象

Abstract

本研究以多孔球模型為基礎，探討其振盪電泳與介電泳行為。多孔球擁有廣泛的應用價值，尤其像是許多生物粒子(DNA、RNA、蛋白質)都屬聚電解質之範疇，因此在生物醫學領域常見其重要應用，如DNA疫苗、基因轉殖(gene delivery)、藥物釋放…等。為了使相關應用及研究更有效率進行，在微小尺度下如何控制粒子運動便成為相當重要的課題！ 振盪電泳相較於一般直流電泳，除了待測物不需要稀釋之優勢外，還多了頻率之調控參數，且在測量上也較為方便，更可避免焦耳熱效應的產生，降低實驗誤差。而介電泳相較於電泳，更能夠精準的操控粒子的移動，對於捕抓或分離之程序上，更能夠有效的執行。進而幫助實驗者有效地提升實驗效率。且愈貼近真實系統的理論模型，在實際應用上才更能準確預測結果。 多孔球在交流電場下的振盪電泳運動，影響電雙層內離子分布，也影響dipole coefficient與有效偶極矩強度。從結果中發現，振盪電泳速度量值與dipole coefficient呈現正相關，因為速度越快，電雙層極化效應越明顯，使得偶極矩越大。介電泳有操控粒子運動的強大能力，而美中不足之處在於：欲達到相同預期效果之操作條件，會因不同系統而有所不同，且往往需要一連串的測試才能達成。本文的研究目標是影響介電泳作用力的關鍵因子─dipole coefficient，其代表粒子在介質中的有效極化程度。吾人使用電動力學模型來描述電解質溶液中帶電的多孔粒子，研究其周圍電雙層與外加電場的交互作用，以及有效偶極矩在不同操作條件下的變化。本研究主要探討的參數為：電雙層厚度、電荷密度、多孔球摩擦係數、介電常數、外加交流電場頻率等。

The electrokinetic behavior of porous sphere is investigated, including dynamic electrophoresis and dielectrophoresis (DEP). Many bioparticles such as potein, DNA and RNA are belonged to polyelectrolyte which has great application in biomedical field and is well modeled as charged porous spheres. So it is important to know how to control the motion of these particles in the small scale system efficiently. Compared with electrophoresis, dynamic electrophoresis is driven by alternating current (AC), which has advantage of convenience of measure and prevention of Joule heating effect. To manipulate particle more precisely, dielectrophoresis(DEP) has a great performance in trapping and separation. Dielectrophoresis, the migration of a dielectric in a non-uniform electric field, has grabbed a great deal of interest in micro/nano-technologies such as microfluidic devices, biomaterial and lab-on-a-chip. However, relevant theoretical researches are still limited. In addition, there exist various kinds of particles other than traditional rigid one, including polyelectrolyte and biological cells, which cannot be modeled as rigid particles. The electrophoretic motion seriously influences the electric double layer and thus polarizability. Positive correlation between dipole coefficient and the particle’s mobility is found because of double layer polarization. DEP has a powerful ability to manipulate particle precisely, but needs a series of experimental tests to fit our demand. So we will study dipole coefficient, which is the most important parameter of DEP, to help to increase experimental efficiency. We use electrokinetic model to describe a charge porous sphere behavior in an electrolyte solution and subjected to an alternating electric field. Dipole coefficient is calculated as a function of the double-layer thickness, charge density, friction coefficient, permittivity and the electric-field frequency.