Numerical Analysis of Electrokinetic and Dielectrophoretic Phenomena in Microchannels

Abstract

Electrokinesis and dielectrophoresis are two technologically important transport phenomena produced by an external electric field applied to a conductive fluid containing biomolecules or bioparticles. Electrokinesis including electroosmosis and electrophoresis is transports of particle or fluid with net mobile charges and is caused by the external electric field. In contrast, dielectrophoresis is particle motions caused by an electric field gradient on an induced dipole moment of the particle and the surrounding fluid. We predict electrokinetic and dielectrophoretic flows in microchannels with a uniform post array. Computational studies are performed to determine particle velocities driven by electrokinesis and dielectrophoresis, and Monte Carlo simulations are conducted to visualize the particle motions. At low applied electric fields, electrokinesis and diffusion is the dominant transport mechanism. At moderate applied fields, dielectrophoresis are balanced with electrokinesis and diffusion, resulting in flowing filaments of concentrated and rarefied particles in the microchannels. At high applied fields, dielectrophoresis overwhelms and locally traps particles. These results provide useful insight for optimizing design parameters of a microfluidic chip for biochemical analysis and especially for development of on-chip sample pretreatment techniques using electrokinetic and dielectrophoretic effects.