旅波介電泳幫浦的設計分析

Design/Analysis of Traveling Wave Dielectrophoresis Pump

葉祐銘(Yu-Ming Yeh)

指導教授 ： 李雨

國立臺灣大學/工學院/應用力學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.10265

摘要

本文所探討之旅波介電泳幫浦基本上為一矩形截面的直微流道，在其一或二個相對壁面上建置有如鐵軌枕木般的平行微電極陣列，在每一電極上施予適當相位的交流電，可對流道中電中性微粒(如血球)產生旅波介電泳力，驅使其移動，並透過黏滯阻力，拖曳其週遭流體，而達到幫浦的輸送功能。本文針對此一幫浦，共完成了如下工作：(1) 電場分析是本文的第一步，針對電場本文完成了一以傅立葉級數來表示的分析解及數值解計算程式，可快速了解不同電極設計的電場變化。(2) 當幫浦的操作頻率飄離最佳設計頻率(CM因子實數部份為零的頻率)，傳統負介電泳力會對進入電極上方區域前的微粒施予一與旅波介電泳力相反之力，阻礙其進入而使幫浦效能降低，甚或使之失效，而為設計高效能旅波介電泳幫浦首要克服者，經由分析及計算，本文提出一項有效的解決辦法，乃是在電極區進口處加進兩片"輔助電極"，相位分別為90∘, 270∘或180∘, 270∘，並把施加在輔助電極上電壓值適度降低，就測試案例，可使原本流道出口平均流速由100μm/s，增加到160μm/s，增加率為60%。(3) 上述幫浦輸送效能的評估及計算須藉助含電場的二相懸浮流的計算，本文修改前人計算程式使包含懸浮微粒對微粒週遭流體電性的影響，並對不同幫浦參數進行數值模擬。在長流道(3000µm)的模擬，輔助電極協助下，施加電壓6V，頻率10MHz，其流道上壁面的微粒x方向平均速度為13.46 µm/s，而陳銘昌(2007)的實驗結果為15 µm/s，二者差異約10%。總括而言，旅波介電泳幫浦為一項有效傳輸二相懸浮流(如血液)的微幫浦，本研究有助提昇該幫浦的分析及設計能力。

關鍵字

旅波 ； 介電電泳 ； 幫浦效能

並列摘要

The traveling wave dielectrophoretic pump studied in this thesis is essentially a straight micro channel with electrode array(s) built on one or two of its walls. A traveling wave electric field is generated inside the channel when an ac field is applied to the electrodes with suitable phase shift between neighboring electrodes. A generalized dielectrophoretic force, including both the traditional and traveling wave dielectrophoretic force, is imparted on the suspended dielectric particles in fluid (such as our cells in blood) inside the channel. Under suitable conditions, the particles move along the channel. As the particles move, they drag their neighboring fluid, and thus the whole medium is delivered (the two phase suspension medium is being pumped). This goal of this thesis is to study such a pump, and several works were completed. (1) The electric fields for different electrode arrangements have been solved via analytical and numerical method. (2) When the pump is operated at frequency shifted from its optimized design frequency (when the real part of the Clausius-Mossotti factor equals zero), the traditional dielectrophoretic force will exert a force to the particles, which is opposite to the driving traveling dielectrophoretic force, when they entered the region above the electrode region. Such opposite force slows down the particles which degrade the pumping efficiency, or even blocks the particles which make the pump fails. In order to overcome such a drawback, a remedy is proposed, which is to add two assistant electrodes before the electrode array. When the assistant electrodes are operated at phase 90 and 270 or 180 and 270 (0 for the first electrode of the array) at a suitable voltage less than that of the electrode array, the opposite traditional dielectrophoretic force can be reduced. Also the pumping efficiency is enhanced with the assistant electrodes. At optimized design frequency, the average velocities of particles at the pump exit are 100 micron/s and 160 micron/s, respectively, for a typical case without and with assistant electrodes. (3) Calculation of two-phase suspension flow under the electric field is required for studying the pumping efficiency. We have updated an existing computer program by modifying the boundary conditions for particle impact and including variable electric properties and of the fluid, which are crucial for a correct simulation. For a typical case with assistant electrode, the numerical average velocity of the particles at exit accounting for the variable electric properties is 13.46 micron/s, which is about 10% less than the corresponding experimental result, 15 micron/s.

並列關鍵字

traveling wave ； dielectrophoresis ； pump performance

參考文獻

[24] 孫志璿， “以旅波介電泳驅動的二相懸浮槽流的數值研究”，國立台灣大學應用力學研究所碩士論文，2004.

[25] 林永錡， “微流道中以旅波介電泳方式驅動的二相懸浮流”，國立台灣大學應用力學研究所碩士論文，2005.

[26] 陳銘昌， “旅波式介電幫浦之實驗研究”，國立台灣大學應用力學研究所碩士論文，2007.

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