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