On the elements of E-textiles : Fabrication and characterisation of textile routing and electrodes

Abstract: “Smart textile” as a notion was demarcated approximately 25 years ago, leading to an enthusiastic hype around the research. Both academic efforts and members of the maker community developed prototypes and artistic creations that incorporated smart features into textiles. From the start of this research era, numerous authors suggested that smart textiles had the potential to revolutionise the healthcare sector. At around the same time, the European Commission had started raising concerns about the demographic trends in Europe, with an ageing population and decreasing birth rates. The need for long-term solutions to address the predicted increase in healthcare demands became evident. Despite 25 years of research with many papers suggesting a soon-to-come commercial breakthrough for smart textiles, such a breakthrough has yet to be seen. There is only a handful of smart textile products on the market currently, and the much-anticipated improvement in the healthcare sector promised by smart textile research is still absent. At the time of writing this thesis, the European Standardisation Committee (CEN) expresses the view that part of the reason for the lack of a commercial breakthrough for smart textiles is the absence of regulations and standards. Technical reports and testing standards regarding smart textiles are being issued continuously by both the International Electrotechnical Committee (IEC), the CEN and the International Organization for Standardization (ISO). These organisations also strive to harmonise the issued guidelines. It is crucial that these regulatory documents describe metrics that are relevant to the applications. Moreover, if easily adopted textile-friendly methods for producing smart textile elements were available to potential producers, in addition to these regulations, the preconditions for a less financially risky market with better functioning smart textile products could be established. This, in turn, might stimulate an increase in the production of smart textile products intended for personalised health. This thesis summarises several aspects of smart textile intended for personalised health (P-health). It provides both suggestions on how to test elements of the textiles properly (their interface with the human body) and how to manufacture components of a smart textile system, such as electrodes and electrical routing. The main objectives of the work behind this thesis include: 1) investigating how functional building blocks for smart textile garments intended for p-health can be manufactured in a textile-friendly way and 2) investigating how to characterise these building blocks in the most appropriate way. It is concluded that such building blocks can be produced and used for smart textile garments in both daily life activities and therapeutic situations. The thesis demonstrates the production of electrically insulated routing integrated into a textile fabric, all done in a single textile production step. For the measurement methods, it is argued that skin-electrode impedance between human subjects and textile electrodes should be measured in-vivo using a three-electrode setup. Additionally, the thesis proposes that instead of measuring sheet resistance, it is better to measure the resistance of the specific smart textile element, as it is shown that sheet resistance is not always applicable to conductive fabrics made from interlaced conductive yarns.