Sheath Free Three-Dimensional Particle Focusing Using Electro-Hydrodynamics

A conventional flow cytometry is a crucial and versatile instrument that measures the fluorescence and light scattering of individual cell and other particulate or molecular analytes in biomedical research. Recently, there have been many efforts to achieve this conventional flow cytometry on lab-on-a-chip devices powered by microfluidics. One of the key techniques of this instrument is to hydrodynamically focus samples within the sensing area of optical systems in order to optimize detection signals. Recent three-dimensional focusing methods using MEMS technology contain sheath flows with very complex channel geometries. In the present investigation, we demonstrated 3-D particle focusing in a single straight micro-capillary without sheath flows using electro-hydrodynamics. Particle beam was successfully made with a beam diameter of about 10 μm for rigid particles. Proposed device provides critical solutions for simple and innovative 3-D particle focusing method for the applications to the MEMS-based micro-flow cytometry.