Studies of particle levitation in a dielectrophoretic field-flow fraction–based microsorter

Abstract

We study particle levitation in a dielectrophoretic field-flow fraction (DEP-FFF) flow sorter by using theoretical and numerical methods. By balancing DEP forces with gravitational and buoyant forces, one can obtain the analytical solution for the particle levitation height. Numerical simulation is carried out and used to compare with the analytical prediction. One can find that there exists a maximum particle levitation height at a specific electrode width (d) for each applied voltage. The maximum levitation height happens at hp/d=0.95. The particle behaviors can be discussed based on the ratio between levitation height (hp) and the width of electrode (d). When levitation height is higher than hp/d>0.6, simulation results show excellent agreement (less than 2% error) with the first-order approximated analytical solution. When levitation height is between 0.43<hp/d<0.6, the results start to show the large discrepancies (more than 2% error) between simulation and the first-order approximated analytical solution. A higher order theoretical solution has to be considered for this situation. When levitation height is hp/d<0.43, particles will stick on the bottom wall. Approximate theoretical solution is no longer applicable.