SMART BIOMECHANICAL TEXTILES FOR WELLBEING AND BIOMEDICAL APPLICATIONS

Abstract

Smart textiles have been drawing more and more attention for decades as they retain features including flexibility, breathability, and lightweight for daily wearable applications. To cope with various functional requirements, their electrical and mechanical behaviours have become the crucial needs, especially for wearable sensors with long-term use. Ti3C2Tx MXene, as a new group of two-dimensional materials after graphene, is well-known for its outstanding electrical and mechanical performance owing to the composition of transition metal carbides, nitrides, or carbonitrides. The abundant functional groups on the MXene surface, including hydrophilic terminations, promise good dispersion in a wide range of solvents. This also facilitates its appearance in the manufacture of smart textiles using different coating techniques. However, the latest findings stated out the Ti3C2Tx MXene degradation issue because of oxidation, which not only triggered additional steps in the manufacture process of MXene-based textiles to meet the expected functional performance, but also leaded to more material wastes. Herein, in this thesis, two easy-operated and efficient coating methods were studied to achieve highly electrically conductive MXene-coated silk yarns regardless the production scale. The coated yarns maintained good flexibility and strength, and thus a woven fabric based Ti3C2Tx MXene tensile strain sensor was fabricated to provide stable, durable, and anti-interference electric signal with wide sensing range. Specifically, by using design of experiment (DoE), we found both solution concentration and soaking time had significant effects on yarn performances during the dip-coating process. After optimising the setup, MXene-coated silk yarn obtained low electrical resistance (~25.6 ohms/cm) with a 23% increase in breaking strength (~107 MPa). As for pad-dyeing technique, on the other hand, solution concentration showed unsignificant effect while soaking duration and padding pressure maintained significant. The pad-dyed yarn had even lower resistance (~15.7 ohms/cm), further improved tensile strength (~111.5 MPa), and it responded in up to 60% resistance change syncing with the relative humidity change in the range of 40% to 90%. It was selected as weft yarn and plain-weaved into fabrics in various widths and lengths with elastic nylon as warp. All MXene-based strain sensors demonstrated superior sensing capability (maximum gauge factor of 14 in strain 0-53%) comparing to those made in the same weave structure, same dimensions but using commercial silver-coated nylon yarn as weft instead. The weave pattern effect on sensors properties was revealed by further comparisons between plain- and twill-woven MXene fabrics. As a result, twill structured MXene sensor had a maximum gauge factor of 16 in wider stain range of 0-80%. In addition, it exhibited stable electrical response during 3000 cycles of loading-unloading stain and excellent anti-interference performance to ambient variables including humidity, compression and bending. Hence, the proposed strain sensor can promise a consistent and durable output dealing with working conditions in daily wear scenarios. In general, this research has not only characterised and functionalised MXene-silk yarn with inexpensive, efficient techniques which reduced the impact caused by material degradation, but also constructed it into woven fabric as a wearable tensile strain sensor. The high functional performed sensor is eligible for health monitoring, body motion detecting and many other purposes.

Date of Award	20 Nov 2024
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Xuqing Liu (Co Supervisor), Yi Li (Main Supervisor) & Max Migliorato (Co Supervisor)