Capacitive effect of coplanar electrodes partially outside the microchannel region for underwater microfluidic-based sensor

This work aims to obtain the capacitance resulted from the coplanar electrode configuration meant to be used for underwater sensing application. Coplanar structure is proposed to overcome the complexity of parallel electrode microfabrication processes which require repeating process of layer deposition. Work is achieved through Finite Element Model (FEM) using ANSYS 12.1 and the result is compared with analytical equation for validation purpose. The model is then modified geometrically to investigate the effect of extending the electrodes beyond the microchannel region. This is due to a very small size of microchannel which sometimes requires the electrodes to be fabricated at larger dimension to increase the detection capability. The result shows that for the specified design (methanol as microfluidic material and PDMS as body structure), electrode width is not a dominant factor that contributes to the detection capability if located outside the microchannel region. Beyond the microchannel region, even the electrodes width is increased, the capacitance value seems to be decreasing.