Microsensor for the Measurement of Concentration of Liquid Solutions

Abstract

This work consists on the design, fabrication and characterization of a sensor to measure the concentration of a liquid solution with dielectric components. The sensor is of capacitive type, and it is processed using conventional microfabrication techniques. A thick interdigital structure made of nickel was electroplated on an alumina substrate. In this way, the interdigital structure forms the capacitor plates while the liquid solution is the dielectric material. The dielectric constant of the solution has an intermediate value when compared to the respective values of the pure components of the mixture. Such microsensors have been successfully applied to distinguish amongst different types of fuels commonly used in Brazilian automobiles (gasoline and ethanol).