The use of metamaterial type double-sided resonator structures in humidity and concentration sensing applications

In this study, the applications of ordinary double-sided split ring resonator (DSRR), double-sided L-type resonator (DLTR) and double-sided closed-cross-ring resonator (DCCR) structures in humidity sensing of chickpea powders and in concentration sensing of methanol-deionized water solutions are studied both in numerically and experimentally for five different samples in each case in microwave S- and X-bands. For the sensitivity analyses, the transmission spectra (i.e. vertical bar S-21 vertical bar) of the sensors are obtained by using rectangular hollow waveguide setups and the dependence of the resonance frequencies on the percentage humidity of chickpea powders or volume fraction of methanol in methanol-deionized water solutions have been recorded. The results show that the DLTR structure is more sensitive than DSRR in both sensing applications in both frequency bands under magnetic excitation. On the other hand DCCR has found to be more sensitive than DSRR for the humidity sensing of chickpea powders and DSRR has found to be more sensitive than DCCR for the concentration sensing of methanol-deionized water application under electrical with normal incidence. It is believed this study provides significant contributions to the sensor literature by introducing specially designed double-sided topologies (i.e. DLTR and DCCR) for two different applications, using special methodologies depending on the application, using two different excitations and two different frequency bands in the characterization. (C) 2019 Elsevier B.V. All rights reserved.