Manipulation of particle motions and their segregation in micro-fluidics by positive dielectrophoresis

We study the ac-field-driven segregation of positively polarized particles flowing through a micro-channel. Our batch fabrication technique allows one to construct an apparatus featuring a large number of mechanically robust and chemically inert micro-devices having a very low ratio of the dielectrophoretic time to the fluid residence time. Experiments were performed on dilute suspensions in microfluidics with electrodes of different sizes arranged parallel and perpendicular to the flow. The application of a high-gradient strong ac field to a flowing suspension results in trapping particles in the channel. When the channel characteristics meet certain requirements, the predictions of a single-particle model for the particle accumulation along the channel are found to be consistent with the experimental data. The model calculations required no fitting parameters because the suspension properties were measured independently. The results of our studies validate a simulation model needed for the design and operation of dielectrophoretic micro-fluidics.