Saw-tooth slot antenna sensor for dielectric characterization of alcohols, saline solutions, and glucose

Abstract

In this study, a low-profile and saw-tooth-shaped slot antenna sensor is proposed for liquid characterization, demonstrating sensitivity to dielectric variations in glucose, saline, and alcohol-based solutions. The antenna consists of a single-layer Rogers 4003C substrate with a rectangular slot integrated with multiple saw-tooth perturbations on the top side and a modified microstrip feedline with a quarter-wavelength transformer on the bottom side. The saw-tooth geometry enhances electric field concentration within the slot region, thereby improving sensitivity to variations in dielectric properties. When liquids with different dielectric constants are deposited on the saw-tooth region of the antenna, measurable resonance frequency shifts occur, enabling material detection. The sensor demonstrated sensitivity in detecting methanol, ethanol, isopropyl alcohol, saline, and glucose solutions. This configuration with dimensions 48 × 48 × 0.508 mm3 (0.78 λo × 0.78 λo × 0.0083 λo at 4.9 GHz, λo represents the free-space wavelength evaluated at the center frequency of the antenna's impedance bandwidth) feasibility for chemical characterization and biomedical sensing applications using an antenna structure.