Temperature-Enhanced Ultrahigh-Sensitivity Microwave Microfluidic Sensor Based on Composite Right/Left-Handed Transmission Lines

In this study, a novel temperature-coordinated sensing system is proposed for microwave liquid sensing. By actively incorporating temperature as a controllable and tunable sweeping parameter, the system establishes a multidimensional measurement space that significantly enhances the sensor’s ability to detect subtle concentration variations in low-concentration aqueous mixtures. To validate this approach, a microwave sensor based on composite right/left-handed transmission lines and integrated with interdigital capacitors was designed, fabricated, and tested. Experimental results demonstrate that the concentration-based frequency detection resolution for identifying a 5% ethanol concentration increased significantly from 4.6 MHz/% to 59 MHz/%, while for a 10% ethanol concentration, it rises from 4.7 MHz/% to 33.7 MHz/%, corresponding to a nearly tenfold resolution improvement.