A metamaterial-based dielectric sensor for characterization of ethanol/1-pentanol binary liquid mixtures at dual bands

This study presents the design, implementation and validation of a metamaterial-based dual-band dielectric sensor in a WR-229 microwave waveguide to determine complex dielectric constants of different concentrations of ethanol/1-pentanol mixture. The sensor consists of a metamaterial and a liquid reservoir. The metamaterial is composed of a step-shape resonator and asymmetrically located split-ring resonators. It is shown that the resonance frequencies do not always decrease as the concentration of ethanol in the binary mixture increases due to hetero-interactions among the constituent solvent molecules. When the volume ratio of the ethanol/1-pentanol mixture is changed from 10 to 90%, 55 MHz and 117 MHz frequency shift is recorded for the lower frequency band around 3.20 GHz and upper frequency band around 4.85 GHz, respectively. A first-order model relating the resonance characteristics with the complex permittivity is deployed to determine the complex dielectric constants at the dual bands. Validity of the sensor and the used model is confirmed by a good agreement. The frequency detection resolutions are found to be 12.6 MHz/Δεr and 26.5 MHz/Δεr for the lower and upper frequency bands, respectively. The results show that the proposed sensor has a good sensitivity and hosting appealing features, such as being cost-effective, easily implementable, non-contact, reusable and non-invasive.