FFSC-based sensors for non-invasive real-time glucose monitoring

This paper presents the design, modeling, and experimental validation of a Fringing Field Sensing Capacitor (FFSC)-based sensor for non-invasive real-time glucose monitoring. The proposed sensor is integrated with a notch filter operating within the 0.5 to 1 GHz frequency range, where glucose concentration-dependent dielectric variations influence the fringing electric fields. These variations induce measurable shifts in the magnitude of the transmission coefficient (|S21|), which are detected using a Vector Network Analyzer (VNA) and processed in real time using a dedicated system. The sensor enables both in vitro testing using glucose samples in a beaker and non-invasive detection by finger placement on the sensing area. An Equivalent Circuit Model (ECM) is developed to accurately characterize the sensor's electrical behavior. Compared to conventional invasive methods, the FFSC approach offers a contact-based, skin-friendly alternative that avoids penetration, enhancing user comfort and enabling continuous monitoring. Simulation and experimental results confirm the sensor's high sensitivity, linearity, and reliability, establishing it as a strong candidate for wearable and battery-efficient glucose monitoring systems in diabetic care.