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Abstract

This thesis presents innovative advancements in bioimpedance technology, focusing on the development and validation of systems tailored for accurate, reliable, and portable skin health assessment and a broad range of biomedical applications. By identifying and addressing the limitations inherent in current bioimpedance methods such as limited bandwidth, reduced accuracies due to phase errors, operator dependencies, and limited portability, this research introduces novel architectures designed to minimize systematic errors, thereby enhancing the clinical applicability of bioimpedance technology.

The study begins by outlining the clinical and research motivations for advancing bioimpedance technology, particularly for skin health monitoring. A comprehensive examination of the electrical properties of biological tissues, with emphasis on skin, establishes a strong theoretical foundation. This groundwork supports the investigation into clinical diagnostic innovative circuit designs, skin hydration multimodal approaches, and error mitigation techniques. This research integrates bioimpedance with optical assessment techniques to develop a hybrid system for skin diagnostics, demonstrating the advantages of multimodal sensing in providing a more comprehensive evaluation of skin hydration and overall skin health.

Key contributions of this thesis include assessment of skin hydration using a multimodal approach, analytical comparison of bioimpedance systems, the development of a Phase Error Compensated Synchronous Demodulation (PECSD) system and an Adaptive Howland Current Source (AHCS) with Automatic Gain Control (AGC). Additionally, the thesis presents a method for assessing cell integrity under haemolytic conditions.

The experimental results indicate that the AHCS significantly improves measurement accuracy by addressing bandwidth limitations in conventional Mirrored Enhanced Howland Current Source (MEHCS), enhancing stability and accuracy across frequencies up to 3 MHz, and maintaining consistent current output even at lower current amplitudes of up to 100μA. The PECSD system further enhances accuracy by reducing phase errors in the synchronous demodulation system from over 21% to below 5%. Experimental validations highlight these systems' effectiveness in applications such as skin health diagnostics including skin hydration monitoring, and cell integrity assessment in the case of skin cancer, underscoring their versatility and robustness for real-time clinical diagnostics.

In summary, this thesis advances bioimpedance technology, making it a more precise and adaptable tool for non-invasive diagnostics. The proposed innovations hold promising potential for broad clinical applications, particularly in dermatology and tissue viability assessment, positioning bioimpedance as a valuable technology of next-generation diagnostic tools.

Publication Type:	Thesis (Doctoral)
Subjects:	Q Science > QP Physiology R Medicine > RL Dermatology T Technology > TK Electrical engineering. Electronics Nuclear engineering
Departments:	School of Science & Technology > Department of Engineering School of Science & Technology > School of Science & Technology Doctoral Theses Doctoral Theses

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