用以輸送血液之旅波式介電泳幫浦

Abstract

本論文以實驗方式探討輸送二相懸浮流(本文用人類血液)之旅波式介電泳幫浦。本幫浦基本上為一直微流道，流道截面為矩形，在其一壁面上一段區域鋪有枕木狀電極，當施以四(或三)個相位差為一組之交流電訊號於電極，傳統式負介電泳將紅血球細胞抬昇遠離電極表面，而旅波式介電泳則驅動紅血球往相位遞增方向前進。隨著血球的移動，會透過黏滯力帶動血漿，經過流力與介電泳力的暫態交互作用，如條件適當，血液可被順利輸送。 我們利用微機電技術來製造該幫浦，並做詳細的參數探討，其中包括操作電壓、頻率、電極間的相位差、電極數量、流道幾何尺寸，以及增強電極的添加與否。在我們的實驗中，人血在流道長度1mm、高度40μm、24根電極、電壓5伏特和20MHz的四相正弦波訊號驅動之下，血球可以15μm/s的速度被輸送。如在原有的電極前加上兩根輔助電極，我們能將流速提升2.4倍。

This thesis studies experimentally the traveling wave dielectrophoretic pump for delivering two-phase suspension medium, using human blood as an example. The pump is essentially a rectangular straight micro channel with a crosstie type electrode array built on one wall and operated under ac voltage with phase shift at neighboring electrodes. Both the conventional and traveling wave dielectrophoresis are generated. The negative conventional dielectrophoretic force repels the red blood cells from the electrode surface and the traveling wave dielectrophoretic force drives the cells along the direction of increasing phase. As the cells move, they drag their neighboring fluid (plasma), and the whole blood is delivered, after some sophisticated interaction of dielectrophoresis and fluid mechanics. The pump was fabricated using MEMS techniques and tested with different parameters of experiment, including the applied voltage, the operating frequency, the phase shift between neighboring electrodes, the number of electrodes, the dimensions of the channel, and the type of enhanced electrodes. It is found that the pump can attain a maximum pumping velocity at an intermediate frequency (about 20 MHz) and channel height (about 40 μm) with four phase signals. The steady average cell velocity can attain 15 μm/s for a pump with 1mm length and 24 electrodes, and operated with a four phase signal at 5 volts and 20 MHz. The pumping performance can be enhanced 2.4 times if two additional electrodes with appropriate applied voltages are added before the regular twDEP array.