A New Permittivity Characterization Methodology for Microwave Filter-Based Microfluidic Sensor

This paper proposes a new liquid permittivity characterization methodology for the microwave filter-based microfluidic sensor: The water-ethanol mixtures with ethanol volume fractions of 10% to 90% in increments of 10% are used as the test liquids. As the test liquids are placed inside the sensing area, the group delay responses of the filter-based sensor are measured to acquire the peak frequencies and corresponding values for complex permittivity computation. Compared with the results using a commercial dielectric probe kit, the maximum measured errors of $\varepsilon_{r}^{\prime}$ and $\varepsilon_{r}^{\prime \prime}$ are 4.7% and 16.15%, respectively.