A novel micro flow cytometer with 3-dimensional focusing utilizing dielectrophoretic and hydrodynamic forces

This paper reports a micro flow cytometer with an innovative 3-dimensional focusing function that can concentrate particles/cells at the center of sample stream, resulting in a high-precision cell counting. Focusing of the sample flow is a critical issue for micro flow cytometers while counting the particles/cells using a buried optical waveguide. Appreciable errors could occur if the particles are randomly distributed vertically even though they have been focused horizontally. In this paper, a 3-D focusing micromachined flow cytometer is demonstrated using the combination of dielectrophoretic (DEP) and hydrodynamic forces. Three major modules have been integrated on glass substrates to form the microfluidic device, including a hydrodynamically driven flow cytometer, microelectrode arrays for dielectrophoretic forces and etched optical fibers for on-line cell detection. With this approach, cells with different sizes could be counted without fluorescence labeling and delicate optical alignment procedures are not required. Experimental data show that high-precision particle/cell counting could be achieved.