Transition-tapered coplanar sensor employing semi-arc cut resonators with dual perforated arrays for enhanced EM glucose detection

This paper presents a novel compact coplanar microwave glucose sensor operating in the 2.0-2.5 GHz band, designed on a thin Rogers RO4003 substrate (ε_r = 3.38, thickness = 0.5 mm) to achieve high sensitivity in a miniature footprint. The proposed sensor incorporates a tapered coplanar transition that progressively channels electromagnetic energy into a miniaturized rectangular sensing region of only 23.5 mm × 16 mm. The core sensing patch features symmetric semi-arc cutouts on its upper and lower edges and a central perforation matrix (15 × 6 holes), while a tides-shaped perforated patch (15 × 4 holes) is positioned on the backside directly beneath the sensing area. This dual-layer perforated architecture introduces a new working principle based on field compression and multi-path perturbation resonance, where semi-arc discontinuities enhance local surface current curvature and the paired hole arrays create vertically coupled resonance channels. The combined effect intensifies the electric-field confinement within the sensing region and amplifies dielectric perturbations caused by glucose-induced permittivity changes. Experimental validation was performed using both deionized aqueous glucose solutions and chemically mimicked blood serums. In all cases, the sensor exhibited high sensitivity (roughly 40 MHz/mg.mL⁻¹ and 130 MHz/mg.mL−1 in aqueous glucose and mimicked blood glucose solutions in clinically relevant glucose range), demonstrated by distinct frequency shifts and measurable magnitude variations corresponding to incremental glucose concentrations. Multiple measurements showed a strong near-linear correlation between the resonant frequency response and glucose levels, confirming excellent repeatability and stability. The compact geometry, efficient field-focusing transition, and the proposed multi-path perturbation mechanism enable reliable microwave glucose sensing, positioning this sensor as a promising candidate for future next-generation low-cost biomedical diagnostic platforms.