Development of interdigitated capacitor sensors for direct and wireless measurements of the dielectric properties of liquids



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The miniaturization of chemical and biological sensors has received considerable attention in recent years for medical diagnostics, environmental monitoring, pharmaceutical screening, military applications, etc. One interesting area of development in microfluidic system is detecting dielectric properties of MUT (Material Under Test) using IDC (Interdigital Capacitor) electrodes. The IDC chemical sensor has been investigated by many researchers because they are cheap to manufacture and can be easily integrated with other sensing components and signal processing electronics. This dissertation presents the design, fabrication, and testing of an IDC (interdigital capacitor) electrode sensor for a fluid property monitoring component that can be integrated into a microfluidic system. One practical point of this research is the analytical evaluation of the interdigital electrode capacitance for the detection of conductivity and permittivity of the aqueous solutions, which is not apparently analyzed in other chemical sensor applications. In addition, a new noble methodology of remotely accessing the IDC sensor by wireless inductive coupling similar to EAS (Electronic Article Surveillance) tags is presented.