Particle separation in alternating-current electro-osmotic micropumps using field-flow fractionation

Abstract

This work presents a novel method for continuous particle separation on the microscale by means of field-flow fractionation. It is based on the use of asymmetric interdigitated electrode arrays on the channel bottom, which induce an electro-osmotic channel flow when driven harmonically. Suspended particles are influenced by viscous fluid drag, sedimentation as well as by dielectrophoretic repulsion forces from the driving electrodes due to the emerging electric field. The significant dependance of the present forces on particle properties allows for separation with respect to particle density and size. This work analyzes electric and flow field by means of the finite element method and investigates the size and density dependent particle motion as a function of driving voltage and frequency of the electrode array. Matching these driving parameters permits the separation of sedimenting particles by their density independently from their size as well as the separation by size. Finally, channel designs are proposed which enable standard separation by means of selective particle mobility in the channel, separation in terms of opposing motion directions, as well as continuous lateral separation.

Dielectrophoretic Field-Flow Microchamber for Separation of Biological Cells Based on Their Electrical Properties

“…At the flow rate of 30 l min, this would correspond to 0.41 mm/s for heat-treated cells, and to 0.35 mm/s for normal ones, so that over the 8 cm length of the channel the normal cells would accumulate a lag of about 12 mm behind the heat-treated ones. In this estimate, we assume that the velocity of the cells is equal to the velocity of the medium, which is based on theoretical considerations detailed in [41], [42].…”

Density-dependent particle separation in microchannels using 3D AC-driven electro-osmotic pumps

“…Thus the presented theoretical approach goes beyond prior studies [12], where the dielectrophoretic particle dynamics produced by symmetric electrode arrays is perturbed by the advection of a superposed, quasi-steady convective flow. For a comprehensive treatise of our theoretical approach the interested reader may be referred to [19]. While gravitational and buoyancy forces are uniformly distributed across the channel, dielectrophoretic forces are strongest above the electrodes.…”

Characterization of Polymerized Liposomes Using a Combination of dc and Cyclical Electrical Field-Flow Fractionation

“…CyElFFF was first investigated by our group to overcome the low effective field found in normal or dc ElFFF. , In CyE1FFF, the electric field is varied during the course of the run (i.e., an ac field is used instead of the constant dc field used for normal E1FFF). − The use of an ac field causes the particles to move cyclically between the walls rather than being accumulated at one wall, as indicated in Figure . The elution of the particles is dependent upon the applied voltage, the applied frequency, and the electrophoretic mobilities of the particles.…”