Comparative Analysis of Geometries of Interdigitated Capacitive Sensors for Liquid Media Detection

This work presents a comparative analysis of interdigitated capacitive sensors aimed at investigating the influence of geometry on capacitive sensitivity in response to variations in the relative permittivity of the dielectric medium. Three geometric configurations—rectangular, circular, and semicircular—were modeled and simulated using the Finite Element Method in COMSOL Multiphysics. Simulations were conducted considering relative permittivity values ranging from 1 to 100. The analysis was based on normalized capacitance, expressed as capacitance per unit area ($\mathrm{pF} / \mathrm{cm}^{2}$), to ensure a fair comparison between geometries with different surface areas. The results showed that all geometries exhibited an approximately linear relationship between capacitance and relative permittivity. However, the rectangular geometry demonstrated the highest capacitive variation, yielding an average sensitivity of $0.25 \mathrm{pF} / \mathrm{cm}^{2}$ per unit of permittivity. In comparison, the circular and semicircular geometries showed average sensitivities of $0.14 \mathrm{pF} / \mathrm{cm}^{2}$ and $0.09 \mathrm{pF} / \mathrm{cm}^{2}$ per unit of permittivity, respectively. These findings indicate that the rectangular configuration is the most suitable for applications involving the monitoring of liquids with different dielectric properties, representing a promising solution for capacitive sensors applied to water quality control.