Permeability negative split square resonator for solid materials dielectric constant and aqueous solution pH sensing applications

Abstract

Metamaterials (MTMs) offer unique electromagnetic properties with wide-ranging applications in microwave sensing. This work introduces a unique approach for non-invasive pH level measurement in aqueous solutions and dielectric properties sensing in solid materials. Mu Negative (MNG) Metamaterial with transmission line and rejection band shifting techniques are utilized for this sensing. The MTM unit cell comprises coupled split square resonators arranged in a 4 × 4 unit cell array with a transmission line underneath. The compact unit cell and array sizes are 0.3 λ × 0.3 λ × 0.06 λ and 1.6 λ × 1.6 λ × 0.06 λ, respectively. The sensor demonstrates impressive performance, with a narrow half-power bandwidth (HPBW) of 0.09 GHz and a high Q-factor of 135.22 for dielectric constant sensing of the solid material. It also achieves an HPBW of 0.38 GHz and a Q-factor of 37.3 for pH sensing. The proposed pH sensor achieves a high sensitivity of 6.15 (MHz/pH). Additionally, the MTM sensor boasts a substantial Figure of Merit (FoM) of 8.311 for solid materials and 16.2 for pH measurements. These promising results are validated through measurements, highlighting the potential of MTM sensors to revolutionize microwave sensing across various applications.