Microchip flow cytometry using electrokinetic focusing

Flow cytometry of fluorescently labeled and unlabeled latex particles is de monstrated on a microfabricated device. The latex particles were detected a nd counted using laser light scattering and fluorescence coincidence measur ements. Sample confinement was accomplished using electrokinetic focusing a t a cross intersection, and detection occurred 50 mu m downstream from the intersection. Particles with diameters of 1 and 2 mu m were analyzed and di stinguished from each other based on their light scattering intensity and f luorescence. A maximum sample throughput of 34 particles/s was achieved, Sa mple mixtures with varying proportions of fluorescently labeled and unlabel ed particles were also analyzed and found to be within experimental error o f the expected ratios.