Fibre optic humidity and pH sensing for healthcare and sports applications

Gomez, David (2019) Fibre optic humidity and pH sensing for healthcare and sports applications. PhD thesis, University of Nottingham.

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The ultimate objective of this PhD thesis is the development and characterisation of optical fibre sensors for humidity and pH monitoring with the aim of exploring their applications in healthcare and sport. In particular, wound healing monitoring, foetal blood sampling and body sweat rate during exercise were explored. Sensors have been thoroughly characterised to establish key parameters such as sensitivity, response time, cross sensitivity to temperature, wearability and portability of the sensors.

The humidity sensor was fabricated by coating the central unclad section of a polymeric optical fibre with a hydrophilic film consisting of PAH/SiO2 layers deposited by layer-by-layer method. The developed sensor achieved a sensitivity of -3.87x10-3 and -9.61x10-3 in transmittance percentage per relative humidity (RH) percentage for the range of ~10% to ~75% RH and 90% - 97% RH, respectively with a response time of 1.5s. Moreover, the implementation of this sensor within garments has been studied to monitor humidity on the human skin. The results suggested the feasibility of the optical fibre sensor to be embedded into garments, such as wound dressings in order to provide humidity measurements of the wound surface without removing the dressing and hence disturbing the wound healing process. In addition, the humidity sensor performance was also tested in the monitoring of the humidity expelled from the body while cycling producing promising results that can lead to the use of this sensor in sports clothing to evaluate in real-time the humidity of the body and hence personalise exercise routines and improve body performance.

Moreover, the optical fibre pH sensor was fabricated with a U-shape geometrical configuration. The sensitive region of the sensor was coated with a dye compound (TSPP) as a pH indicator using sol-gel technique. This sensor was based on the absorbance of light in two regions of the spectra (Soret and Q bands) over small pH variations providing a sensitive pH range of 6.7 - 8.1. The sensitivity obtained was 0.032 in absorbance units per pH unit and -0.054 in absorbance units per pH units for the Soret and Q band, respectively. The potential application for this sensor is to equip clinicians with the tool that can help to take an early decision during foetal blood sampling technique since the sensor developed can provide in-situ pH measurements with a fast response (~40s). In addition the optical fibre sensor for pH measurements can be useful to analyse the properties of the sweat or wound exudate in order to provide more information to improve nutrition and wound healing, respectively.

On the other hand, the instrumentation to monitor the response of both sensors was also investigated. The design of a low-cost portable electronic device consisting of small electro-optical components for the evaluation of the developed sensors is presented to replace the relatively bulky experimental set-up consisting of a CCD spectrometer and a broadband light source and provide a small electronic unit to monitor in real-time the sensors response.

In conclusion, the research presented in this PhD offers a novel alternative for the current techniques and devices implemented in healthcare and sports applications through the development of optical fibre sensors for humidity and pH measurements.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Morgan, Stephen P.
Korposh, Serhiy
Hayes-Gill, Barrie R.
Keywords: Optical fibre sensor, humidity and pH sensor, healthcare applications, wound healing monitoring, foetal blood sampling, sweat rate, electronic portable unit
Subjects: T Technology > TA Engineering (General). Civil engineering (General) > TA1501 Applied optics. Phonics
Faculties/Schools: UK Campuses > Faculty of Engineering
Item ID: 55406
Depositing User: Gómez, David
Date Deposited: 18 Jul 2019 04:40
Last Modified: 07 May 2020 12:02

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