Characterisation of knitted conductive textiles for wearable motion sensor applications

Isaia, Cristina (2018) Characterisation of knitted conductive textiles for wearable motion sensor applications. PhD thesis, University of Nottingham.

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Combining stainless steel with polyester fibres adds an attractive conductive behaviour to the yarn. Once knitted in such a manner, fabrics develop sensing properties that make them suitable for wearable applications as a consequence of the variation of their conductivity when subject to structural deformations. The use of such textiles as accurate strain/motion sensors can be considered the new frontier in wearable sensor applications, in opposition to their use as simple strain/motion detectors as mainly done until now.

This thesis aims to characterise the electrical properties of knitted conductive textiles made of 20% stainless steel and 80% polyester fibres in the context of their application as fabric strain sensors. However, the use of conductive textiles as sensors is challenging and requires the combined study of their electrical and mechanical behaviours.

In the first part of this thesis, the fabric resistance variation is analysed with a purposely built measurement system during a considerable number of stretch-recovery cycles performed by an Instron tensile machine. From the resulting electrical characterisation, it is possible to select the best knit pattern candidates for the second part of the study, which regards their integration into a supporting garment and further investigation of their electrical and mechanical properties in view of their application as wearable motion sensors.

Two acquisition systems capture both free and constrained motions of a participant's knee and the electrical resistance variation due to combined deformation of samples and supporting leggings. In both parts of this thesis, a detailed analysis in terms of linearity, stability, sensitivity and hysteresis confirms that the overall sensing performance progressively decreases during extended use as a consequence of the short-term irreversible fabric deformation and does not significantly recover after short rest periods.

For the development and use of high performance fabric-based strain sensors, it is therefore evident the importance of the long-term maintaining of a reversible stretch-recovery behaviour not only of the sensing fabrics but also of the supporting garments they are integrated in.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Branson, David
McNally, Donal S.
Keywords: knitted conductive textiles; fabric strain sensors; wearable sensing technology
Subjects: Q Science > QC Physics > QC501 Electricity and magnetism
Faculties/Schools: UK Campuses > Faculty of Engineering
Item ID: 55329
Depositing User: Isaia, Cristina
Date Deposited: 08 Jan 2019 11:36
Last Modified: 08 Feb 2019 08:01

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