交流電滲流應用於微幫浦之元件研究

Abstract

中 文 摘 要 本論文探討以交流電滲流為原理利用平面非對稱電極陣列在微尺度下驅動電解質溶液。交流電滲流的成因可歸因為平行於平面電極的電場分量與鄰近電極表面之帶電離子的交互作用。基於由Ramos所提出之理論分析，在電極表面流體流動速度分佈可解出【7】。數值計算結果說明由電極之非對稱性可推動流體往特定方向流動。實驗方面，電極陣列以電子束蒸鍍金/鉻於玻璃底材上，再以微影蝕刻製程定義其幾何；微流道由軟微影製程中Replica molding技術製作。實驗結果驗證氯化鉀溶液（10-4M）可由67對非對稱電極陣列所驅動。 實驗結果顯示氯化鉀溶液被驅動方向會受到施加電壓（1 to 9 volts peak to peak）與/或頻率（100Hz to 100kHz）影響。在較高電壓與/或較高頻率的操作條件下，幫浦推動方向為由寬電極往窄電極方向且可能成因為faradaic process。相反地，在較低電壓與較低頻率，幫浦推動方向與先前相反且其成因為在電極上形成之電雙層。在分別以faradaic與non-faradic效應為主的幫浦推動下，流體速度皆超越20微米/秒。此外，在固定頻率1kHz下，亦觀察到流體流動在某特定電壓下改變其方向的現象。

ABSTRACT Pumping of electrolyte solution in micro scale, by planar asymmetric electrode array, based on AC electro-osmosis (ACEO) is reported in this thesis. The principle of ACEO flow is attributed to interaction between the component of electric field parallels the electrode surface and ions adjacent to the electrodes. Based on theoretical analysis proposed by Ramos et al. [7], distribution of flow velocity on electrode surface is calculated. Numerical results show that pumping can be achieved by asymmetry electrode geometry. Experimentally, the microfluidic chip is fabricated by electron beam evaporation, with Au/Cr on glass substrate, for the electrode array and replica molding via soft lithographic technique for the micro-channel. Total of 67 pairs of asymmetric electrode array to pump KCl solution (10-4M) are demonstrated. Results show that pumping direction can be controlled by tuning the excitation voltage (1 to 9 volts peak to peak), and/or frequency (100Hz to 100kHz). Higher voltage, and/or frequency, results in pumping direction from wide to narrow electrode – indicative of faradaic process. Conversely, non-faradaic process occurs with lower voltage and/or frequency, which causes reversal in pumping direction and is attributed to electrical double layer forming on electrode surfaces. Maximum pumping velocity is over 20μm/sec for both faradaic and non-faradaic processes. In addition, transitional potential that causes a change in pumping direction is observed under a fixed frequency of 1kHz.