Microwave Microfluidic Sensor Using Microstrip Line Terminated with LC Resonators

This paper presents a sensor for dielectric characterization of microfluidic samples at microwave frequencies using a microstrip transmission line terminated with series a LC resonator. The series LC resonator is implemented with a capacitive patch etched out of the ground plane, which is connected through a via hole to a thin metallic trace on the top surface implementing an inductor. Applying a fluidic sample to the PDMS microchannel aligned with the capacitive patch modifies the resonance frequency and notch depth in the reflection coefficient of the sensor. The dielectric properties of the liquid sample can be estimated by establishing a mathematical relation between the resonance characteristics and the sample complex permittivity.