A Highly Sensitive Dual-Band RF Glucose Sensor with Diamagnetic Metasurface Transitions

Abstract

For microwave glucose sensing without a vector network analyzer (VNA), one of the options is to measure the reflection coefficient of a glucose sensor using a gain-phase detector. Gain-phase detectors have a frequency threshold, and, in the case of AD8302, the threshold frequency is 2.7 GHz. In this work, focus has been placed on realizing a glucose sensing device compatible with AD8302. Methodology: A sensing device with two resonant frequencies below the threshold frequency of AD8302 was realized on a lossy FR4 substrate in a way to allow the measurements to be cross-checked within a narrow frequency range. The realized sensor features the use of two closely packed periodic arrays of closed metal rings in the energy transfer region. On the other hand, a near-Littrow configuration was successfully used in the sensing region for detection of ultra-low concentration of glucose in a liquid solution. The fabricated sensor has exhibited dual resonances, with one resonance occurring at around 2.42 GHz and the other occurring at around 1.65 GHz. The minimum detectable glucose concentration of the proposed glucose sensor was found to be 25 mg/dL. The sensitivities that have been achieved were 715 kHz/(mg/dL) at around 2.42 GHz, and 805 kHz/(mg/dL) at around 1.65 GHz. Overall, a glucose sensing device with a dual resonant frequency characteristic has been realized with a minimum detectable glucose concentration at 25 mg/dL and a maximum sensitivity at 805 kHz/(mg/dL).