Optical microflow cytometer for particle counting, sizing and fluorescence detection

A novel on-chip optical flow cytometer concept is reported for fluorescence detection, enumeration, and sizing of microparticles in a poly-dimethylsiloxane (PDMS) microchip. The detection system integrates a pair of external optical fibers and other optical components for particle counting, sizing and fluorescence analysis in each measurement simultaneously. The scattered light signal indicates the total number and the size of the particles passing through the detection window, whereas the concurrent backward fluorescence signal shows only the number of fluorescence particles. In the experiments, microparticles of four different sizes with diameters ranging from 3.2 to 10.2 μm were discriminated and counted based on the fluorescence and scattered light intensity. The relative percentage of the fluorescence-labeled particles can be analyzed by the ratio of the events of fluorescence signals to forward scattered signals.