Fluid flow study of an AC electrothermal micropump consisting of multiple arrays of microelectrodes for biofluidic applications

Abstract

Electrokinetics has many applications in a wide range of areas, such as lab-on-a-chip and biomedical microdevices. The electrothermal effect has been used for biofluid delivery systems since it has high pumping efficiency for high conductive liquids (>0.1 S/m) compared to other electrokinetic techniques such as electroosmosis. AC electrothermal (ACET) micropumps are based on the temperature gradient caused by Joule heating or an external heat source, which generates permittivity and conductivity gradients in the bulk of the liquid. When the liquid is subjected to an electric field, the ACET force is created. Electrode geometry significantly affects the electric field distribution, which can yield stronger ACET forces. Previously electrode dimension optimization has been performed for a single-array coplanar asymmetric configuration in order to obtain maximum ACET velocities. In this paper we expand the study to other governing parameters in a multiple-row microelectrode array configuration consisting of microelectrodes placed on top, bottom, and/or side walls of a microchannel. The studied parameters are the substrate material and thickness, ambient temperature, fluid viscosity, and actuation frequency. Electrode dimensions remain constant during the study (120 μm wide and 20 μm thin electrodes, 20 μm gap). The study is performed using finite element analysis software for one pair of microelectrodes on each array with periodic boundary conditions. The simulation data is then compared with experimental data for a single combination of the aforementioned parameters. The results show that the effect of these parameters on ACET flow can be significant.