Analysis of Electrokinetic Flow in Microfluidic Chips

Abstract

Miniaturization and integration of conventional bioassay laboratory procedures into the micro-fabricated Lab-On-Chips (LOCs), usually referred to as Micro Total Analysis (μTAS) systems , have tremendous impacts in the fields of genomics, proteomics, and other clinical analysis. Electrokinetically driven flow offers efficiently and effectively to control flow in micro devices without a need for any mechanical components. These bioanalytical microsystems utilize electrokinetic mobility including electroosmosis and electrophoresis modes for transport, mixing, manipulation, separation and detection of sample analytes. LOCs are already proven to significantly reduce analysis time and sample volume sizes without requiring a skilled worker to operate. In addition, LOCs are inexpensive, versatile, robust as well as portable. At the solid surfaces of the microchannel walls, an oppositely charged thin layer is formed separate from the bulk solutions of the sample analytes and buffer solutions. This thin layer is referred to as an Electrical Double Layer (EDL) or simply called Debye's Thickness Layer . Based on the type and material of the electrode surface, it is formed either by negatively or positively charged ionic groups from the bulk solution at the wall's surfaces. Using commercially available finite element software, called COMSOL Multiphysics , the electric field is modeled in such a way that it displaces EDL formed by ionic liquid leading to generate an electrokinetic flow in the microchannel. MEMS (Micro-electromechanical systems) and Chemical Engineering Modules of COMSOL are employed to model, physics set up, and simulate the ionic fluid flow for the analysis of fluid propulsion and chemical mass transport for the various physical models of microchips. The ionic fluid concentrations and velocities are plotted against the potential differences across the sample inlet vs. the outlet and across the buffer inlet vs. the outlet, respectively. Based on the COMSOL Multiphysics simulation results, it was co