Abstract
Wearable electronics have increasingly garnered attention across numerous fields, ranging from biomedical devices for disease diagnosis, therapy, and healthcare monitoring to neuroscience applications like brain-computer interfaces and electroencephalography, as well as energy harvesting and personal entertainment technologies such as virtual reality. However, the prevalent commercial wearable devices remain predominantly rigid and bulky, suffering from poor skin integration due to the significant mechanical stiffness of components like printed circuit boards or plastic casings compared to the softness of human skin. This stiffness often compromises signal fidelity and limits user mobility and comfort, making such devices unsuitable for continuous daily wear.In contrast, epidermal electronics represent a breakthrough in flexible wearable technology. These devices adhere directly to the skin surface, offering a seamless interface for extracting physiological and physical data, thus facilitating easy interaction with the human body and enabling prolonged monitoring. Epidermal electronics mimic the properties of human skin, featuring extreme deformability, lightweight, and compatibility with soft tissues. These devices can monitor the body's physical, chemical, biological, and environmental parameters with high precision and minimal interference. Unique to this technology are features like biodegradability and self-healing capabilities, which are not possible with traditional, rigid wafer-based electronics. This type of flexible electronic system can be classified into various forms, including electronic patches, electronic tattoos, and electronic ink, based on their physical characteristics. Despite recent advancements in creating thin and well-integrated electronic patches, they still face limitations regarding their inability to be customized in terms of shape and size for specific applications. Conversely, electronic tattoos offer a solution to this issue by pre-fabricating and tailoring the desired morphology prior to application on the skin. However, the complexity of the fabrication process and the requirement for transfer printing during deployment pose challenges to their conformability with the skin. On the other hand, electronic ink allows for on-demand customization by directly writing onto the targeted epidermal area. Nevertheless, electronic ink typically has a limited shelf life, and exposure to sweat on the body surface can cause its performance deterioration, detachment, or even failure.
This thesis includes the development of epidermal electronics for human body motion tracking and healthcare monitoring with advanced materials, ingenious design, and simple fabrication methods. Firstly, based on percolation theory, the conductivity model of carbon-based composites was proposed in this thesis, which offers valuable insights into the processing and manufacturing of innovative carbon-based composite sensors for the studies of electronic slime (E-slime) and the sinewave corrugated structure-based flexible sensor (the SCS sensor). Inspired by the biological reshapability and environmental adaptability of amoeba, an ultra-deformable, bioadhesive, strong self-healing, and electromechanical-durable wearable E-slime is proposed, which can instantaneously form on-skin electronics in situ to detect body motion and physiological signals. E-slime demonstrates desired sensing performance with high sensitivity, wide sensing range, and low detection limit, which can seamlessly adhere to the skin and can be easily reused multiple times. E-slime also enables on-the-fly deployment of motion monitoring tasks at various body locations, showcasing its versatility and reliability for body motion recognition and personal health monitoring. Besides, Inspired by the structure of the stripes of marine angelfish, the SCS sensor was proposed, boosting both mechanical and electrical properties for enhanced motion detection and biomechanical monitoring. The sensor is fabricated by embedding multi-walled carbon nanotubes and carbon blacks into a PDMS matrix, achieving high electrical conductivity and mechanical robustness. It exhibits desired sensitivity and flexibility, making it ideal for healthcare monitoring and human-machine interfaces.
In summary, we innovate the design, fabrication, and functionality of epidermal electronics for human body motion tracking and healthcare monitoring. We believe that this thesis will open a broad possibility for epidermal electronics in practical applications.
| Date of Award | 4 Sept 2024 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Yajing SHEN (Supervisor), Jun LIU (Supervisor) & Wen Jung LI (Supervisor) |