電動力輸送在側流輔助之奈米過濾及熱輔助膠體檢測上的應用

Abstract

近年來，薄膜製備技術的飛速發展使得薄膜孔徑大小得以達奈米級別，展現出極具應用價值的微觀特性。其中，與薄膜孔徑大小相當的電雙層賦予孔道離子選擇性，使其在奈米過濾、整流、發電、膠體檢測等領域得到廣泛應用。 在奈米過濾領域中，過去文獻主要聚焦於單一孔道之除鹽研究，而忽略離子濃度極化及孔與孔之間相互作用的影響。本研究探討多孔道薄膜的過濾性能，且發現多孔薄膜常伴隨著嚴重的離子濃度極化現象使得過濾效能嚴重下降。為解決這一問題，引入側流輔助消除入口端的離子濃度積累。 結果表明，側流流速越大，過濾能力越強，但超過特定值后提升效果趨於平緩，表明大部分離子積累已得到去除。此外，通過擬合數據點，調查過濾能力與側流流速之間的定量關係，系統地闡述了流速對過濾能力的提升作用。 在此類奈米流體裝置的研究中，另一個重要的研究主題為膠體檢測。透過施加電位之電泳行為來捕捉溶液中的膠體對其進行分析。這類應用面臨的兩大挑戰為提高捕捉速率與減低遷移速率，這兩者往往是難以兼顧的。為此，我們對一電泳系統施加溫度梯度，討論溫度梯度對其造成的影響。結果顯示，單純施加溫度梯度之熱泳系統會使奈米孔道兩端產生誘發的電位差引發電滲流。施加電位與溫度場時，一帶負電之球形膠體置於溶液時，同向的溫度梯度與電位梯度可以在幾乎保持同樣的遷移時間的前提下，顯著降低捕捉膠體所需時間來達到更好的捕捉效率。

The rapid development of thin-film preparation techniques has enabled the fabrication of thin films with nanopore sizes, opening up new avenues for the exploration of their unique microstructural properties and potential applications. Among these, the electrical double layer, with a thickness comparable to the pore size, imparts ion selectivity to the nanochannels, rendering them promising candidates for a wide range of applications, including ion filtration, rectification, power generation, and colloid detection. In the nanofiltration field, previous studies have primarily focused on the single nanopores, neglecting the influence of ion concentration polarization (ICP) and inter-pore interactions. This study delves into the filtration performance of multi-pore thin films, revealing that ICP poses a significant challenge, leading to a substantial decline in rejection. To address this issue, a cross-flow is introduced to assist in eliminating the accumulation of ions at the inlet of the nanopore. The results demonstrate that as the cross-flow velocity increases, the rejection also enhances. However, beyond a specific value, the improvement in performance becomes less pronounced, indicating that the majority of ion accumulation has been effectively removed. Furthermore, by fitting the experimental data, a quantitative relationship between rejection and cross-flow velocity is established, providing a systematic understanding of the velocity in enhancing rejection In the context of nano-fluid devices, colloid detection stands as another critical research area. Electrophoresis, induced by an applied potential, serves as a powerful tool for capturing and analyzing colloids in solution. However, this application faces two major challenges: achieving high capture speed while maintaining low translocation velocity. These two objectives often conflict, as increasing capture rates typically results in faster translocation, while reducing translocation velocity compromises capture efficiency. To address this challenge, a temperature gradient is introduced into the electrophoresis system, and its impact on the system's performance is investigated. The results reveal that a thermophoresis system, solely driven by a temperature gradient, generates an induced potential difference across the nanochannels, leading to electroosmotic flow. When both an electric potential and a temperature field are applied, for negatively charged spherical colloids suspended in the solution, an aligned temperature gradient and electric potential gradient can significantly reduce the time required for colloid capture while maintaining a similar translocation velocity.