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UBC Theses and Dissertations

Design and evaluation of textile electrodes for biological signal monitoring Le, Katherine


Developments in electronic textiles (e-textiles) have focused on integration into remote physiological monitoring systems. This has encompassed functionalized textile sensors for continuous biopotential signal collection. This research examines structural hierarchical effects in e-textiles to understand properties influencing the performance of e-textile sensors. Electrocardiography (ECG), a bioelectric signal associated with electrical activity of the heart muscle, was selected for evaluating e-textile electrode performance. The structure-property relationships of fibre and yarn to fabric systems were investigated for silver (Ag)-nylon textiles. Fibre geometry and yarn twist were found to impact yarn linear resistance, and electrode contact impedance at the fabric level up to limiting values. Influencing factors at the yarn level were explained by contact between fibres in the yarn structure, yarn specific volume, fibre volume fraction, and orientation angles. At the fabric level, influencing factors included yarn diameter, fibre packing, and apparent contact area of the electrode. Skin-electrode interfacial interaction, and relationship to biopotential signal quality were characterized through surface roughness and skin contact impedance measurements of knitted electrodes. Compatibility at the skin-electrode interface was impacted by skin hydration, roughness, and applied pressure. A high throughput roll-to-roll system was developed to produce electrochemically coated silver/silver-chloride (Ag/AgCl) yarns, and the process was characterized. Electrodes were fabricated through embroidery of Ag/AgCl yarns. The performance of Ag/AgCl e-textile electrodes was compared against embroidered Ag e-textiles, and standard Ag/AgCl electrodes. The Ag/AgCl e-textile electrodes demonstrated excellent ECG signal quality, and high stability based on polarization potential measurements when compared to Ag e-textiles. Durability of e-textiles for long-term use was addressed through the development of a stretchable, self-healing, biocompatible and recyclable chloride-based ionogel coating. The material was employed as a cast film, and sprayable e-textile coating, applied to strain sensing and biosignal recording, respectively. The ionogel film demonstrated high recovery of material properties after a 30-minute healing period at room temperature and reformed after abrasion to a coated e-textile surface by the addition of ethanol. Electrical properties of ionogel coated electrodes met specified performance ranges for e-textile electrodes. The methods and findings presented in this dissertation can be used to guide e-textile electrode materials selection and design.

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Attribution-NonCommercial-NoDerivatives 4.0 International