Designing and analysis of flexible four legged-loaded metamaterial absorber sensor for permittivity detection of a solid substrate

This article proposes a metamaterial absorber (MMA) based sensor with solid permittivity analysis. MMA application has received significant interest across multiple domains, including sensors, wireless communication, detectors, emitters, antenna design, and spatial light modulators. The suggested absorber consists of circular and rectangular split-ring resonators with an inner four-lagged loaded copper patch. This configuration is designed to produce a distinct resonance at 2.615 GHz. The associated absorption rate at this resonance is 99.98 %. The study involved the extraction and subsequent analysis of the complex values related to the permittivity, permeability, refractive index, and impedance of MMA. There is no significant change in reflection and transmission coefficients for 15° bends of array and unit cell, due to which the proposed MMA can be used for conformal applications. The validity of the sensor is analyzed by comparing between known and measured permittivity of the Roger substrate. The average and normalized sensitivity are 107.55 MHz and 4.113 %. The sample thickness is finalized from 0.4 to 1.4 mm on the basis of the reflection coefficient of the sensor shifted linearly towards lower frequency. Sample thickness analysis is crucial for any sensor model. However, most reported articles have unnoted this analysis. Additionally, the sensor is equipped with an un-metalized Roger RT5880 dielectric slab with nine 1.5 mm (diameter) holes. The holes caused Roger RT5880′s dielectric constant to change; the sensor effectively traced the change in the sample’s dielectric constant. Overall, the proposed material exhibits a high absorption efficiency, miniature size (29.4 × 29.4 mm 2 ), low cost, simple structure, and can resist the environmental factors that cause cross-sensitivity, making it an attractive candidate for permittivity sensors for solid substrates.