A Terahertz Metamaterial Sensor With Graphene Resonator for Ethanol‒Water Concentration Sensing

This paper presents a terahertz metamaterial sensor designed to detect changes in ethanol concentration in water, which is highly relevant for chemical analysis, food safety, and biomedical sensing applications. The sensor comprises three distinct layers: a graphene‐based resonator at the top, an intermediate dielectric spacer layer, and a metallic layer at the bottom, forming a compact and efficient absorber structure. The sensor exhibits an absorption of 99% at a resonant frequency of 6.08 THz for 0% ethanol concentration, with a quality (Q) factor of 31.48. Furthermore, the effects of various graphene material parameters, such as chemical potential and relaxation time, on absorption performance have been systematically investigated through numerical simulations to achieve an optimal response and enhanced sensing performance. As the ethanol concentration increases, the resonant frequency gradually shifts to lower values due to the rise in the effective refractive index near the sensing region, enabling reliable refractive index discrimination. The proposed sensor achieves a high figure of merit (FOM) of 12.4, indicating excellent resolution for refractive index detection, along with a sensitivity of 2369 GHz/RIU and a full width at half maximum (FWHM) of 190 GHz. These results demonstrate that the proposed graphene‐based terahertz sensor offers a promising platform for high‐resolution, noncontact liquid sensing in the terahertz frequency regime.