Modelling and simulation of an insulator-based DEP microdevice

The current work presents a finite element method (FEM) model of a microchannel for particle separation using dielectrophoresis (DEP). The model is based on the commercial software COMSOL and Matlab was used to postprocess the FEM results. The microchannel layout consists of an array of insulating cylindrical posts in the midsection of the microchannel, etched in glass. The microchannel was filled with a ionic solution whose pH and conductivity were fixed to known values, by adding NaOH and K2HPO4. A series of experiments had to be conducted. In each experiment, the microchannel was filled with the ionic solution, a sample of fluorescent microspheres was injected in the inlet, and a DC electric field was applied across the channel using Pt electrodes The experiments were recorded using a camera coupled to a microscope. The electrokinetic mobility, which depends on the pH and the conductivity, was estimated using the particle image velocimetry (PIV) method from the captured videos. The insulating posts in the microchannel produce a non-uniform electric field distribution, which in turn generates a dielectrophoretic (DEP) force on the submerged particles. The DEP force competes with the fluid drag force exerted on the particles. At a certain voltage value, particles are trapped. The FEM model used the estimated electrokinetic mobility to predict the trapping voltage and to calculate the particle trajectories. This research work is a preliminary step in characterizing the dielectrophoretic microchannel, whose final target is to be used for the concentration, separation and identification of biological cells.