Optical microflow cytometer based on external total reflection.

A novel optical microflow cytometer based on external total reflection comprising a laser-induced fluorescence system, a PDMS chip, a plane mirror and a dichroic beamsplitter is proposed for the simultaneous detection, enumeration and sizing of labeled and nonlabeled microparticles. In the proposed approach, the total number and size of the particles passing through the detection region is determined via the nonscattered light signal reflected from a plane mirror positioned over the microchip, while the number of fluorescence-labeled particles is determined via the back scattered fluorescence signal. The experimental results confirm the ability of the proposed system to count and size fluorescent and nonfluorescent particles with nominal diameters ranging from 6 to 10.2 μm. In addition, it is shown that for a mixed sample containing both labeled and nonlabeled particles, the number of nonlabeled particles can be determined by subtracting the number of peaks in the fluorescence signal from that in the reflected light signal.