Numerical and Analytical Analysis of a Robust Flow Regulator in Electroosmotic Microfluidic Networks

Abstract This paper proposes a three-way electrokinetic flow regulator to control flow direction independent of the electrolyte solution and regulator material. In this two-dimensional regulator, the flow direction is simply controlled by varying the applied electrical voltage at microfluidic network ends. The performance of the regulator is discussed based on full detailed numerical simulations using the Nernst-Plank equation and a simplified semi-analytical approach. Numerical simulations revealed that the cut off voltage ratio required for switching flow direction is almost independent of the electrical double-layer (EDL) thickness and strongly depends on regulator geometry. A semi-analytical approach is introduced to determine the regulation voltage ratio and dimensionless flow rate during the regulation. It is showed that for thin EDLs, the presented approach can adequately predict the overall performance of the regulator with considerably lower computational efforts. Numerical and analytical approaches introduced in this paper, can be extended to more complex networks e.g. four-way networks.