A low cost MEMS based NDIR system for the monitoring of carbon dioxide in breath analysis at ppm levels

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Abstract

The molecules in our breath can provide a wealth of information about the health and well-being of a person. The level of carbon dioxide (CO2) is not only a sign of life but also when combined with the level of exhaled oxygen provides valuable health information in the form of our metabolic rate. We report upon the development of a MEMS-based non-dispersive infrared CO2 sensor for inclusion in a hand held portable breath analyser. Our novel sensor system comprises a thermopile detector and low power MEMS silicon on insulator (SOI) wideband infrared (IR) emitter. A lock-in amplifier design permits a CO2 concentration of 50 ppm to be detected on gas bench rig. Different IR path lengths were studied with gases in dry and humid (25% and 50% RH) in order to design a sensor suitable for detecting CO2 in breath with concentrations in the range of 4 to 5%. A breath analyser was constructed from acetal and in part 3D printed with a side-stream sampling mechanism and tested on a range of subjects with two data-sets presented here. The performance of the novel MEMS based sensor was validated using a reference commercial breath-by-breath sensor and produced comparable results and gave a response time of 1.3 s. Further work involves the detection of other compounds on breath for further metabolic analysis and reducing the overall resolution of our MEMS sensor system from ca. 250 ppm to 10 ppm.

Item Type: Journal Article
Subjects: R Medicine > RC Internal medicine
Divisions: Faculty of Science, Engineering and Medicine > Engineering > Engineering
Library of Congress Subject Headings (LCSH): Breath tests, Gas detectors, Medical informatics
Journal or Publication Title: Sensors and Actuators B: Chemical
Publisher: Elsevier Science SA
ISSN: 0925-4005
Official Date: 29 November 2016
Dates:
Date
Event
29 November 2016
Published
6 April 2016
Available
4 April 2016
Accepted
28 November 2015
Submitted
Volume: 236
Page Range: pp. 954-964
DOI: 10.1016/j.snb.2016.04.016
Status: Peer Reviewed
Publication Status: Published
Access rights to Published version: Restricted or Subscription Access
Date of first compliant deposit: 6 April 2016
Date of first compliant Open Access: 6 April 2017
Funder: University Hospitals Coventry and Warwickshire NHS Trust
URI: https://wrap.warwick.ac.uk/78361/

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