整合光波導與介電泳的微流粒子計數器

Abstract

本研究利用微機電製程技術，設計並製作出整合光學檢測機構於微流晶片的微粒計數器。當微粒流經整合於晶片上的光纖偵測區時，會對偵測光吸收與散射，其所產生的訊號可以透過自撰程式判斷而測得通過偵測區微粒的個數。要正確計數通過偵測區的粒子，首要將粒子聚焦，使其依序逐顆通過狹窄（本文所研究者約數十微米）的偵測區。雖然目前文獻中已有多項聚焦微粒的微流設計，但其晶片的製程相當繁複，且並沒提供其微粒計數器計數準確率的驗證結果。故本研究的目標為提出一類製程方法相對簡單且價格相對便宜的微粒計數器，該類計數器主以流道幾何作微粒聚焦。另本文亦對所提出的微粒計數器的計數準確率進行實驗驗證。 本研究共提出兩項微流晶片：（1）單層流道與雙層流道接合所形成的三維結構晶片，此晶片純利用幾何結構來達到三維方向的聚焦，本文稱之為三維幾何聚焦晶片或簡稱為三維晶片；（2）單層流道與電極陣列的接合所形成的晶片。此晶片利用幾何結構達到水平方向聚焦，並使用負介電泳力將微粒抬升至光檢測區，本文稱之為二維幾何暨介電泳聚焦晶片，或簡稱為電極晶片。 根據實驗計數訊號的結果，可得知在同種微粒下，較大微粒的光訊號強度變化優於較小的微粒者。而在不同種微粒下，聚苯乙烯（polystyrene）微粒因為透光率比細胞差，故其光訊號強度變化優於細胞者。此外，由於電極晶片能夠藉由調整電壓將微粒控制在流道中央，使得造成的光訊號強度變化較大。在計數準確率的實驗中，我們得到三維晶片與電極晶片皆能成功計數聚苯乙烯微粒、肺腺癌細胞CL1-0與人體結直腸癌細胞Colo205。其中聚苯乙烯微粒的計數準確率可達到98％左右，而CL1-0與Colo205細胞的計數準確率可達到約90％。此外，所設計的晶片能成功分辨並計數不同大小（15與10 μm的聚苯乙烯微粒）及不同種類(聚苯乙烯微粒及Colo205細胞)的微粒，其計數準確率分別達到98％及88%。

MEMS technique is employed to fabricate a micro-fluidic particle counting device using buried optical waveguides for optical detection in this research. A particle blocks the light and lowers its strength via scattering（reflection）and absorption, and thus is counted via a software when it passes through the detection region in the micro-fluidic device. A first step for fabricating a successful counter is to focus the particles so that they pass the narrow detection region（of tens of micros in length in this study）in a one-by-one manner. Although there exist some successful micro-fluidic focusing methods in the literature, the fabrication process and operation are rather complicated. Also the counter accuracy of the micro-fluidic particle counting devices was not reported. The purpose of the present study is to propose two counters using geometric restriction and dielectrophoretic force for particle focusing. The proposed devices are easy to be fabricated, inexpensive, and accurate. Two chips using two focusing methods are studied here. One uses the geometric restriction to achieve the three-dimensional particle focusing, which is simply called the 3D chip. The other uses the geometric restriction to achieve two-dimensional focusing and negative dielectrophoretic force to position the particle to the illuminating detection region, and is called the electrode-chip. According to the experiments, variation of the light signal strength is smaller for smaller particles of the same kind. The variation of light signal strength for cells is lower than that of the polystyrene particles because the transmittance of cells is better than that of the polystyrene particles. The electrode-chip can control the settling height of the particle in the center of channel via the applied voltage so that the variation of light signal strength is bigger. We successfully counted polystyrene particles, lung cancer cells CL1-0 and colorectal cancer cells Colo205 via both the 3D chip and electrode-chip. 98% , 90% and 90% accuracy can be achieved for polystyrene particles, lung cancer cells and colorectal cancer cells respectively. We have also counted mixed particles of different sizes（10 and 15 μm polystyrene particles）and of different kinds (polystyrene and colo205 cells) simultaneously, and 98％ and 88% accuracy can be achieved, respectively.