• Zekun Liu

Student thesis: Phd


Wearable sensors are arousing increasing research interests in recent years due to their great potential in motion detection, personal and public healthcare, future entertainment, man-machine interaction, artificial intelligence, and so forth. Much research has focused on fibre-based wearable sensing devices because of the appealing performance of fibres, including processing flexibility, wearing comfortability, outstanding lifetime and serviceability, low-cost and large-scale capacity. However, some vital performance of the sensing devices in practical applications is still far from optimal, such as wearable comfort, sensitivity, sensing reliability in the fickle microclimate of wearable interfaces and multi-direction dynamic tactile stimulations. This thesis proposes novel design and fabrication of fibre-based wearable pressure, strain, and humidity sensors by the material functionalization approaches of carbonization, in-situ oxidation, and polymer-assisted metal deposition (PAMD). The devices overcome the abovementioned challenges, aiming to construct body sensing networks (BSNs) with high wearing comfort and sensing reliability for monitoring human health and activities. The project mainly focuses on fibre functionalization and sensing device fabrication through many novel approaches for monitoring human health and activities. 1) Breathable wearable pressure sensors are fabricated by directly carbonizing knitted hemp fabrics at high temperatures. Unlike mostly reported pressure sensors made with active materials with the encapsulation of elastomers, the encapsulation-free sensor shows high permeability by taking advantage of the porous structure of the textile. 2) By combining carbonization and the PAMD, a strain sensor made with carbonized linen fabric with copper deposition presents a very high sensitivity (GF~3557.6 in the strain range from 0 to 48%). The concept of improving sensor sensitivity by using two-layer sensing elements can be extended to many sensing devices. 3) This work firstly finds that carbonized fabrics can directly detect humidity, the sensitivity is controllable by changing the oxidation time after the carbonization. The strategy is extendable to many carbonized substates. 4) A strain sensor based on the PAMD and an innovative embroidery technique is developed. The sensor processes both breathability and insensitivity to bending and pressuring inputs. The BSNs based on the developed pressure, strain and humidity sensors show high performance in addressing the issue of complicated wearable mechanical inputs and microclimate changes. This project develops many high-performance, fibre-based wearable sensors via novel fibre functionalization and device fabrication and demonstrates their great application potential in the high-accuracy and anti-jamming BSNs. It proposes many concepts and strategies for wearable sensing devices, which will arouse much attention in the research area of wearable and flexible electronics.
Date of Award31 Dec 2022
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorPatrick Gaydecki (Supervisor) & Yi Li (Supervisor)

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