Validation of Finite Element Model (FEM) of Coplanar Electrodes Capacitive Sensing Using Microfluidic-based Sensor Device

This work aims to validate the 2D Finite Element Model (FEM) for estimating the capacitance changes across a microchannel with coplanar electrodes configuration employed. Such electrodes configuration becomes popular in microfluidic-based application where the sensing activity occurs inside a microchannel. ANSYS 12.1 is used to built the 2D model of the structure. The work begin by building the FEM model to find the capacitance per unit length, C/l or C* of different combination of coplanar structures. The variation yields an error of less than 17% as compared to analytical equation with both models having the same trend of capacitance changes. Then, based on the theory of capacitance in parallel, both models are further verified experimentally using a fabricated sensor device that employs a selected structure combination. Comparing the FEM and analytical model to the experimental measurement, the result shows the error of 5% and 24% for both models, respectively.