Non-invasive glucose monitoring has become a critical area of research for diabetes management, offering a less intrusive and more patient-friendly alternative to traditional methods such as finger-prick tests. This study presents a novel approach using a semi-solid tissue-mimicking phantom designed to replicate the dielectric properties of human skin and blood vessels. The phantom was simplified to focus solely on the skin layer, with embedded channels representing veins to achieve realistic glucose monitoring conditions. These channels were filled with D-(+)-Glucose solutions at varying concentrations (60 mg/dL to 200 mg/dL) to simulate physiological changes in blood glucose levels. A miniature patch antenna optimized to operate at 14 GHz with a penetration depth of approximately 1.5 mm was designed and fabricated. The antenna was tested in direct contact with the skin phantom, allowing for precise measurements of the changes in glucose concentration without interference from deeper tissue layers. Simulations and experiments demonstrated the antenna’s sensitivity to variations in glucose concentration, as evidenced by measurable shifts in the dielectric properties of the phantom. Importantly, the system enabled stationary measurements by injecting glucose solutions into the same blood vessels, eliminating the need to reposition the sensor while ensuring reliable and repeatable results. This work highlights the importance of shallow penetration depth in targeting close vessels for noninvasive glucose monitoring, and emphasizes the potential of microwave-based sensing systems as a practical solution for continuous glucose management.

Environmental conditions, including temperature, humidity, and light, can impact the quality of drugs. Microwave-based approaches offer a fast and cost-effective way to detect quality variations, providing an alternative to traditional techniques in the pharmaceutical and cosmetic industries. This article proposes the use of a microwave sensor for monitoring the quality of pharmaceutical drugs at distinct temperature levels. A small planar sensor based on three hexagonal split ring resonators (TH-SRR) is fabricated. The design is manufactured on an FR-4 dielectric substrate. The sensor is tested on a 1000 mg paracetamol tablet, at temperatures ranging from 40 to 80 $$^\circ$$∘ C. The Variation in the permittivity that characterizes product degradation is translated into a shift in the frequency of the scattering matrix elements. To validate the microwave approach, drug quality is examined with the laser-induced breakdown spectroscopy (LIBS) technique, an optical emission laser used for both qualitative and quantitative investigations of elements contained in a sample. The existing elements are classified using the National Institute of Standards and Technology (NIST) database and categorized according to their spectral line wavelengths. The experiments show the presence of optimal wavelength values for carbon (C), hydrogen (H), nitrogen (N), and oxygen (O) at 247.92 nm, 656.49 nm, 244.23 nm, and 777.48 nm, respectively. The microwave experimental results show a shift frequency of approximately 1 MHz on average when the tablet is heated at 80 $$^\circ$$∘ C for 15 min. Meanwhile, the LIBS measurement shows a remarkable shift in terms of intensity of approximately 8884 and 812 for carbon and hydrogen, respectively. Understanding how paracetamol dries under high temperatures and improving the process settings of the microwave sensor are investigated and assessed in this work.

Temperature control in the industrial use of phosphate ensures chemical stability, which affects product quality and process efficiency. This study introduces a novel approach employing a microwave sensor with a double hexagonal complementary split-ring resonator (DH-CSSR) for Real-Time control and monitoring of industrial phosphate powders, focusing on temperature-induced variations. Operating within the 0.1GHz - 4GHz frequency range, the sensor detects shifts in the resonance frequency of the S-parameters, which are indicative of alterations in the dielectric properties of the phosphate powder as a function of temperature variations. A comparative evaluation with simulated outcomes, incorporating permittivity values ascertained through a coaxial probe at diverse temperatures, establishes a robust congruence between experimental and simulated datasets. Root Mean Square Error (RMSE) values of 0.44, 2.2, and 3.28 for the first, second, and third resonances, respectively, underscore the sensor’s precision in mirroring the actual conditions of phosphate powder encountered during storage and transportation. Such accuracy underscores the sensor’s potential in accurately representing real-world conditions of phosphate powder, thus facilitating the optimization of crop yield through enhanced management of phosphate powder characteristics.

Maintaining engine oil quality is critical for industrial machinery and transformers to ensure efficient operation and reduce the risk of failure. This paper presents a novel application of an X-band microwave sensor, using a third-order electroformed iris waveguide filter, for real-time, non-invasive engine oil quality monitoring. By detecting shifts in the dielectric properties of engine oil, the sensor accurately tracks oil degradation as it ages. Unlike traditional methods that require oil extraction and laboratory analysis, this sensor enables continuous, in-situ monitoring, providing immediate feedback without disrupting system operations. Any change in oil quality causes a frequency shift, as variations in its dielectric properties affect the waveguide’s resonance. This shift can be measured in real time, enabling accurate monitoring of oil degradation. Additional measurements were conducted using the coaxial probe technique to analyze the changes in the oil’s electrical behavior during various heating periods. Experimental results demonstrate the sensor’s sensitivity, with measurable frequency shifts of up to 10 MHz observed in the most aged oil samples. These shifts clearly correlate with the oil’s aging process, confirming the sensor’s potential for practical use in predictive maintenance. This system, utilizing an electroformed waveguide, offers a cost-effective and efficient solution for enhancing machinery longevity and optimizing maintenance schedules in industrial applications.