Dual Mode Microwave Microfluidic Sensor for Temperature Variant Liquid Characterization

A dual mode, microstrip, microfluidic sensor was designed, built, and tested, which has the ability to measure a liquid's permittivity at 2.5 GHz and, simultaneously, compensate for temperature variations. The active liquid volume is small, only around $4.5~μL. The sensor comprises two quarter ring microstrip resonators, which are excited in parallel. The first of these is a microfluidic sensor whose resonant frequency and quality factor depend on the dielectric properties of a liquid sample. The second is used as a reference to adjust for changes in the ambient temperature. To validate this method, two liquids (water and chloroform) have been tested over a temperature range from 23 °C to 35 °C, with excellent compensation results.