A Micro-Fluidic Particle Counting Device Using Optical Waveguides and Dielectrophoresis
Date Issued
2012
Date
2012
Author(s)
Pan, Hong-Cheng
Abstract
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.
Subjects
micro particle counter
biochips
optical detection
accuracy for particle counting
SDGs
Type
thesis
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