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This paper presents a fully passive and wireless glucose concentration sensor that integrates a capacitively coupled complementary split-ring resonator (CSRR) with an H-slot UHF RFID antenna. The CSRR serves as the primary sensing element, where changes in glucose concentration alter the effective permittivity of the surrounding solution, thereby modifying the resonator capacitance and shifting its resonance behavior. Through near-field capacitive coupling, these dielectric variations affect the antenna input impedance and backscatter response, enabling wireless sensing by modulating the maximum read range. The proposed sensor operates within the 902–928 MHz UHF RFID band and is interrogated using commercial RFID readers, eliminating the need for specialized laboratory equipment such as vector network analyzers. Full-wave electromagnetic simulations and experimental measurements validate the sensor performance, demonstrating a variation in the read range from 6.23 m to 4.67 m as glucose concentration increases from 50 to 200 mg/dL. Moreover, the sensor exhibits excellent linearity, with a high coefficient of determination (R2=0.986) based on the curve-fitted data. These results underscore the feasibility of the proposed sensor as a low-cost and fully portable platform for concentration monitoring, with potential applications in liquid characterization and chemical sensing.

This paper introduces a flexible loop antenna-based sensor optimized for real-time monitoring of meat quality by detecting changes in dielectric properties over a six-day storage period. Operating within the 2.4 GHz ISM band, the sensor is designed using CST Microwave Studio 2024 to deliver high sensitivity and accuracy. The sensing mechanism leverages resonance frequency shifts caused by variations in permittivity as the meat degrades. Experimental validation across five samples showed a consistent frequency shift from 2.14 GHz (Day 0) to 1.29 GHz (Day 5), with an average sensitivity of 0.173GHz/day. A strong correlation was observed between measured and simulated results, as evidenced by linear regression (R2=0.984 and R2=0.974 for measured and simulated data, respectively). The sensor demonstrated high precision and repeatability, validated by low standard deviations and minimal frequency deviations. Compact, printable, and cost-effective, the proposed sensor offers a scalable solution for food quality monitoring. Its robust performance highlights its potential for integration into IoT platforms and extension to other perishable food products, advancing real-time, non-invasive, RF-based food safety technologies.

This paper presents a study on the repeatability of washing effects on two antenna-based sensors for breathing monitoring. One sensor is an embroidered meander antenna-based sensor integrated into a T-shirt, and the other is a loop antenna integrated into a belt. Both sensors were subjected to five washing cycles, and their performance was assessed after each wash. The embroidered meander antenna was specifically compared before and after washing to monitor a male volunteer’s different breathing patterns, that is, eupnea, apnea, hypopnea, and hyperpnea. Stretching tests were also conducted to evaluate the impact of mechanical deformation on sensor behavior. The results highlight the changes in sensor performance across multiple washes and stretching conditions, offering insights into the durability and reliability of these embroidered and loop antennas for practical applications in wearable health monitoring. The findings emphasize the importance of considering both washing and mechanical stress in the design of robust antenna-based sensors.