結合介電泳現象與微過濾去除溶液中低濃度奈米粒子之研究

Abstract

介電泳效應是利用不均勻的電場，藉由溶液中的粒子與溶劑被極化的程度不同，使粒子在溶劑中移動的現象。傳統的研究中常應用此方法於低通量、高濃度微米粒子的分離，然而隨著各領域對高通量、低濃度奈米粒子分離的需求不斷增加，在回顧了以往使用介電泳效應操控溶液中粒子以達到分離的相關研究及其局限，並比較不同研究結果後，我們提出結合介電泳效應與微過濾，期望通過我們的實驗設計實現對溶液中低濃度奈米粒子的高效分離。 在實驗中，我們首先使用黃光微影製程製作透明的玻璃微流道來擬似薄膜孔洞，以觀察不同大小及材質的奈米粒子因介電泳效應所產生的分離行為。透過利用COMSOL Multiphysics模擬微流道中的電場梯度分布，並將模擬結果與實驗中粒子的實際分布情況進行比較，以確認粒子的介電泳特性。根據微流道實驗的結果，我們進一步將分離裝置改為微過濾薄膜，將薄膜視為由無數微流道構成的結構，並在薄膜兩邊架設電極，將介電泳效應結合薄膜過濾操作。我們使用水為背景溶液，以50nm的二氧化矽、100nm的polystyrene及5nm的金粒子作為分離目標，並選用孔徑大於粒子直徑10倍以上的薄膜進行分離實驗，發現介電泳效應結合微過濾能有效移除溶液中濃度等級數十至數百ppb的奈米顆粒，且具有同時分離不同介電泳性質粒子的能力，證實結合介電泳效應與微過濾的確能大幅提高過濾通量，並降低過濾壓力及能耗。利用SEM檢視過濾後的薄膜，我們也發現介電泳在加強薄膜過濾的同時，也會使奈米粒子在薄膜表面產生類似濾餅的結構，這是一般過濾奈米粒子時不易產生的現象。最後，我們展望未來的研究，期望能繼續優化此技術，以開發出適用於更小粒徑、且不受粒子與溶劑種類限制，並具有大通量潛力的分離技術。

The dielectrophoresis (DEP) effect utilizes a non-uniform electric field to exert different magnitudes of force on impurity particles and solvent in a solution. Traditional studies have often applied this method for the separation of low-throughput, high-concentration, or larger particles. However, as the demand for high-throughput, low-concentration nanoparticle separation continues to grow across various fields, we plan to combine the DEP effect with microfiltration membrane structures to improve upon previous research and introduce technological innovations. This study reviews prior research that used the DEP effect to manipulate particles in solutions for separation, as well as its limitations. Based on a comparison of different research results, we propose our experimental design, aiming to achieve efficient separation of particles in solutions through microfiltration membranes. In the experiment, we first used photolithography to fabricate transparent glass microchannels to observe the separation behavior of particles under a non-uniform electric field caused by the DEP effect. We then used COMSOL Multiphysics to simulate the electric field gradient distribution in the microchannels, comparing the simulation results with the actual distribution of particles in the experiment to confirm their DEP characteristics. After confirming the DEP properties, we switched the separation apparatus to a microfiltration membrane, treating the membrane as a structure composed of numerous microchannels. Based on the results of the microchannel experiments, we set the operational conditions for combining the DEP effect with membrane filtration. We then conducted experiments using membranes with pore sizes 10 times larger than the particle sizes. The experiments targeted the separation of 50nm silica, 100nm polystyrene, and 5nm gold particles. The results from the DEP effect combined with microfiltration showed good separation performance, demonstrating the feasibility of separating particles with different DEP properties simultaneously, and confirming the method’s viability for purification operations at a laboratory scale. However, some unexpected results occurred during the experiments. We conducted further research to investigate these anomalies and proposed a possible separation mechanism, which was later verified through SEM imaging. Lastly, we look forward to future research, aiming to develop separation techniques suitable for smaller particles, independent of particle and solvent types, and with the potential for high throughput.