Particle electrophoresis and dielectrophoresis in curved microchannels.

Studies of particle electrophoresis have so far been limited to primarily theoretical or numerical analyses in straight microchannels. Very little work has been done on particle electrophoretic motions in real microchannels that may have one or multiple turns for reducing the devices size or achieving other functions. This article presents an experimental and numerical study of particle electrophoresis in curved microchannels. Polystyrene microparticles are found to migrate across streamlines and flow out of a spiral microchannel in a focused stream near the outer wall. This transverse focusing effect arises from the dielectrophoretic particle motion induced by the nonuniform electric field intrinsic to curved channels. The experimental observations agree quantitatively with the numerical predictions.