Flow fractionation of microparticles under a dielectrophoretic field in a quadrupole electrode capillary

A technique of fractionation for microparticles was proposed that utilized a unique combination of a dielectrophoretic (DEP) field generated by a quad rupole electrode and a laminar flow in a capillary of 82.5 mum in radius. T he fabricated capillary possessed four platinum wires in its inside wall as a quadrupole electrode. In a nonuniform electric field generated by the qu adrupole electrode, microparticles, such as polystyrene and carbon, in wate r experienced DEP forces in the radial direction. When a sample solution wa s pumped in, an ideal laminar flow perpendicular to the DEP force was forme d inside the capillary. The microparticles dynamically migrated by the DEP force across the laminar flow while they were carried by the flow. A theore tical model taking the DEP force and the laminar flow pattern into account predicted the elution profiles of the single microparticles quantitatively. The elution times of the microparticles depended on the dielectric propert ies and the sizes of the microparticles, as well as the voltage and frequen cy of the applied alternating current.