球形膠體粒子於多孔流體介質之介電泳現象探討

Dielectrophoresis of spherical colloidal particles in porous fluid medium

曾建鈞(Chien-Chun Tseng)

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(2022年)

https://doi.org/10.6342/NTU202202445

摘要

利用不均勻電場操控介電質運動的「介電泳」(dielectrophoresis, DEP) 常出現在微流體裝置、實驗室晶片等應用中來操縱等於或小於微米尺度的粒子，在化工分離物質的程序上，因介電質造成的極化程度不同，可以用正或負介電泳來簡易分離物質。

其一介電泳分離手法是應用在過濾系統上，此方法是使用多孔介質作為過濾孔洞介質，施加外加電場後，粒子將被孔洞捕捉。為了掌握此系統的介電泳力來提升在分離實驗上之效率，本論文即是探討球型膠體粒子於多孔介質流體的介電泳現象，而使用之多孔介質流體為Brinkman fluid，針對粒子在不同物理條件下所受極化程度進行模擬，預測介電泳動行為，並計算影響介電泳力的關鍵因子─dipole coefficient¬¬，其所代表的物理意義為粒子在介質中的有效極化程度。

我們將透過電動力學模型來描述電解質溶液中的帶電粒子，粒子會於溶液中與周圍電雙層產生隨頻率改變而形成之電雙層動態平衡。介電泳與傳統常見的電泳最大的不同便是多了頻率這項可調控參數，系統其他電動力學參數亦包括：粒子表面帶電量、介電常數比值等。由於粒子存在於多孔介質，我們以Brinkman方程式描述非均相多孔系統中的流力行為，多孔介質層中的摩擦係數將減緩粒子介電泳動度，阻力過大時會有泳動趨於0的情形，更詳細內容將在結果與討論章節做進一步解釋。

關鍵字

介電泳 ； 介電質 ； 交流電場 ； 電動力學 ； 多孔介質 ； 有效偶極矩 ； 介電泳泳動度 ； 電雙層極化效應 ； 電雙層動態平衡

並列摘要

Dielectrophoresis (DEP), which uses an uneven electric field to manipulate the motion of dielectrics, is often used in microfluidic devices, lab-on-a-chip and other applications to manipulate particles on a scale equal to or smaller than microns.

One of the dielectrophoretic separation methods is the use of porous media as the pore medium for filtration. In order to find out the dielectrophoretic force of this system to enhance the efficiency of the separation experiment, this thesis is to investigate the dielectrophoretic phenomenon of spherical colloidal particles in a porous medium fluid, using a porous medium fluid called Brinkman fluid. The effective degree of polarization of a particle under different physical conditions is simulated to predict the dielectrophoretic behavior and to calculate the key factor, dipole coefficient, which represents the physical meaning of the effective degree of polarization of a particle in the medium.

The electrodynamic model is used to describe the charged particles in an electrolyte solution, where the particles are in dynamic equilibrium with the surrounding electric double layer as the frequency changes. The main difference between dielectrophoresis and conventional electrophoresis is the additional parameter of frequency. Other electrodynamic parameters of the system include: the surface charge of the particles, the ratio of dielectric constants, etc. Since the particles are present in porous media, we describe the flow behavior in a non-homogeneous porous system by the Brinkman equation. The drag coefficient in the porous medium will slow down the dielectrophoretic mobility of particle, and when the drag coefficient is too high, the mobility will tend to 0. More details will be explained in the Results and Discussion section.

並列關鍵字

dielectrophoresis (DEP) ； dielectric material ； AC electric field ； electrokinetics ； porous medium ； Brinkman fluid ； effective dipole moment ； DEP mobility ； double layer polarization ； dynamic equilibrium of electric double layer

參考文獻

參考文獻

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