Modeling the Impact of Sensitivity Distribution Variations of Tetrapolar Impedance Configurations in Microfluidic Analytical Devices

Abstract

Goal: The purpose of this work is to investigate the effects of electrode topology and electrode configuration of tetrapole electrical impedance measurement (TEIM) systems used in microfluidic devices. Methods: Two different electrode topologies with fixed dimensions, selected based on reported applications, are investigated. Three dimensional sensitivity maps, generated using finite element modelling (FEM), show fundamental differences in sensitivity distribution between six different injecting and measuring electrode configurations. Transfer impedance values generated for different band sizes and migrating band trains were compared to show the influence of sensitivity distribution on the performance of TEIM used in electrophoresis or cellomics. Results: Fundamental differences of sensitivity distribution between different electrode configurations were detected, with “Inline Dipole” and “Square Across” configurations exhibiting areas of negative sensitivity in the tetrapole centre. This causes baseline impedance differences of up to one order of magnitude and effecting the performance when measuring heterogeneous fluids. Conclusion: The results suggest that certain electrode configurations should be avoided for applications relying on high spatial resolution. Significance: This work demonstrates the significance of impedimetric sensor geometry design in ultimately enabling the miniaturisation of electrophoretic systems towards increasingly portable devices.