Characterization and use of a fiber optic sensor based on PAH/SiO2 film for humidity sensing in ventilator care equipment

Hernandez, Francisco U. and Morgan, Stephen P. and Hayes-Gill, Barrie R. and Harvey, Daniel and Kinnear, William and Norris, Andrew and Evans, David and Hardman, J.G. and Korposh, Sergiy (2016) Characterization and use of a fiber optic sensor based on PAH/SiO2 film for humidity sensing in ventilator care equipment. IEEE Transactions on Biomedical Engineering, 63 (9). pp. 1985-1992. ISSN 0018-9294

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Abstract

Objective: To develop a compact probe that can be used to monitor humidity in ventilator care equipment. A mesoporous film of alternate layers of Poly(allylamine hydrochloride) (PAH) and silica (SiO2) nanoparticles (bilayers), deposited onto an optical fibre was used. The sensing film behaves as a Fabry-Perot cavity of low-finesse where the absorption of water vapour changes the optical thickness and produces a change in reflection proportional to humidity. Methods: The mesoporous film was deposited upon the cleaved tip of an optical fibre using the layer-by-layer method. The sensor was calibrated in a bench model against a commercially available capacitive sensor. The sensitivity and response time were assessed in the range from 5 % relative humidity (RH) to 95 %RH for different numbers of bilayers up to a maximum of nine. Results: The sensitivity increases with the number of bilayers deposited; sensitivity of 2.28 mV/%RH was obtained for nine bilayers. The time constant of the response was 1.13 s ± 0.30 s which is faster than the commercial device (measured as 158 s). After calibration, the optical fibre humidity sensor was utilised in a bench top study employing a mechanical ventilator. The fast response time enabled changes in humidity in individual breaths to be resolved. Conclusion: Optical fibre sensors have the potential to be used to monitor breath to breath humidity during ventilator care. Significance: Control of humidity is an essential part of critical respiratory care and the developed sensor provides a sensitive, compact and fast method of humidity monitoring.

Item Type: Article
Additional Information: (c) 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works.
Keywords: Humidity, Optical fibers, Films, Humidity measurement, Biomedical measurement, Probes, Time factors
Schools/Departments: University of Nottingham, UK > Faculty of Engineering > Department of Electrical and Electronic Engineering
Identification Number: 10.1109/TBME.2016.2521662
Depositing User: Morgan, Steve
Date Deposited: 12 Sep 2017 11:23
Last Modified: 13 Sep 2017 02:43
URI: http://eprints.nottingham.ac.uk/id/eprint/45762

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