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Lubangakene, Innocent (2025) Non-invasive microwave-based sensor system for monitoring hydration levels in patients with electromagnetic waves. Doctoral thesis, London Metropolitan University.
This thesis presents the design, development, and experimental validation of a novel, noninvasive microwave-based biosensor system for real-time hydration monitoring. Addressing a critical need in clinical and wearable health technology, the research explores the use of dielectric properties of human tissues, particularly at microwave frequencies, to detect variations in tissue water content as a proxy for hydration status. Building on prior work from the London Met University Rescaling project, which introduced BaFe-inclusion-based microstrip patch sensors/antennas for enhanced electromagnetic sensitivity, this thesis extends to that concept by developing and optimizing a ferrite-loaded H-slot microstrip patch antenna for non-invasive hydration diagnosis. The sensor operates around 2.2 GHz in the ISM band, ensuring safe, lowpower interaction with the human body.
The system integrates the antenna with a portable vector network analyser (NanoVNA) and a Raspberry Pi running custom Python software for signal processing, visualization, and classification. Extensive human subject testing (N = 425 measurements) demonstrated the sensor's ability to distinguish between hypohydrated, euhydrated, and hyperhydrated states using reflection coefficient (S₁₁) thresholds. Experimental results showed strong agreement with simulation predictions, confirming the inverse relationship between tissue hydration and reflected microwave power. The system achieved high sensitivity, dynamic range, and robustness across varying users and conditions, with minimal influence from confounding factors such as age or sex.
The work validates the feasibility of using reflection coefficient analysis for real-time, noninvasive hydration tracking and paves the way for personalized, continuous health monitoring diagnosis. Specifically, this novel non-invasive approach represents a substantial advancement in the general field of biomedical science by enabling instantaneous hydration status estimation within seconds eliminating the delays, invasiveness, and inaccuracies associated with conventional methods such as blood osmolality testing, urine analysis, or bioelectrical impedance. This rapid and reliable assessment capability provides a new paradigm for clinical diagnostics, sports science, and remote health monitoring, demonstrating how electromagneticbased sensing can deliver precise physiological insights without discomfort or laboratory dependence.
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