Hourglass-Shaped Terahertz Metasurface Exhibiting EIT-Like Resonance for High-Performance Label-Free Glucose Sensing

Terahertz sensing is a promising label-free technique for glucose monitoring due to its sensitivity to biomolecular refractive index changes. However, achieving both high sensitivity and sharp spectral selectivity in compact, on-chip platforms remains a significant challenge. Here we propose an hourglass-shaped terahertz metasurface resonator (HG-MSR) with dual lateral rods that induces a pronounced electromagnetically induced transparency (EIT)-like effect, enabling strong bright–dark mode coupling and a transmission peak of 96% with suppressed radiation loss. Fullwave simulations showthat precise asymmetry tuning of HG-MSR placement modulates the EIT window and field confinement. When applied to glucose sensing across physiological concentration ranges, spanning hypoglycemia to hyperglycemia, the device exhibits spectral sensitivity exceeding 86, 500 nm.RIU−1with excellent linearity of 99.8% to RI changes over a range of glucose concentrations from 54 mg/dL to 342 mg/dL, and a low detection limit suitable for clinical thresholds at the design level. These results demonstrate the feasibility of the HG-MSR as a theoretically promising metasurface architecture for terahertz biosensing. As the present study is entirely simulation-based, the reported performance should be regarded as a proof-of-concept that motivates future experimental validation and system-level implementation. More broadly, because the sensing mechanism relies on generic refractive-index perturbations rather than analyte-specific functionalization, the proposed design framework may be extendable to other biological and chemical sensing scenarios in both aqueous and nonaqueous environments, subject to experimental verification.