Reducing N2O induced cross-talk in a NDIR CO2 gas sensor for breath analysis using multilayer thin film optical interference coatings

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Abstract

Carbon dioxide (CO2) gas sensing is an important aspect in the biomedical field of capnography, where cheap, fast and accurate measurement of exhaled CO2 vs. time is crucial in the evaluation of lung and tracheal function during surgical anaesthesia and is an under-used bio-marker for underlying respiratory conditions. Current detection methods do not adequately meet these requirements and suffer from considerable cross-talk associated with the commonly used anaesthetic gas nitrous oxide (N2O). In this work, we report how cross-talk can be reduced in a commercially available, low power (35 mW) non-dispersive infrared (NDIR) CO2 gas sensor using thin film multilayer optical filters. Current sensor spectral response, spans 2500 nm–5000 nm via use of a pentanary alloy LED/photodiode optopair grown by molecular beam epitaxy (MBE), resulting in sensor sensitivity to gases with absorption bands in this region, including N2O. To reduce the effective spectral response of the sensor, capturing only CO2, a multilayer thin film optical interference bandpass filter has been designed and deposited directly onto the diode epi-structures using microwave plasma assisted DC magnetron sputtering. Three different coating configurations have been explored; LED-only coated, photodiode only coated and both coated. Gas sensor response to N2O for each coating configuration has been explored. It was found that application of an optical bandpass filter onto both the sensor LED and photodiode only was the most effective method of reducing sensor response to N2O, however no signal was observed in one of the two “LED and PD coated”, therefore optimal coating configuration for cross-talk reduction is subject to further investigation.

Original languageEnglish
Pages (from-to)9-16
Number of pages8
JournalSurface & Coatings Technology
Volume336
Early online date14 Sep 2017
DOIs
Publication statusPublished - 25 Feb 2018

Fingerprint

Light interference
Multilayer films
Chemical sensors
Light emitting diodes
Infrared radiation
interference
coatings
Thin films
Coatings
Photodiodes
sensors
Sensors
thin films
gases
Optical filters
light emitting diodes
Bandpass filters
photodiodes
Gases
bandpass filters

Keywords

  • CO2 sensor
  • thin films
  • mid-IR
  • microwave-assisted DC magnetron sputtering
  • multilayer optical interference filter
  • mid infrared light emitting diodes
  • mid infrared photodiodes
  • capnography
  • surgical anaesthesia
  • nitrous oxide
  • cross-talk
  • breath analysis

Cite this

@article{2398d06d9ea04a1d8fb88f3359892e5f,
title = "Reducing N2O induced cross-talk in a NDIR CO2 gas sensor for breath analysis using multilayer thin film optical interference coatings",
abstract = "Carbon dioxide (CO2) gas sensing is an important aspect in the biomedical field of capnography, where cheap, fast and accurate measurement of exhaled CO2 vs. time is crucial in the evaluation of lung and tracheal function during surgical anaesthesia and is an under-used bio-marker for underlying respiratory conditions. Current detection methods do not adequately meet these requirements and suffer from considerable cross-talk associated with the commonly used anaesthetic gas nitrous oxide (N2O). In this work, we report how cross-talk can be reduced in a commercially available, low power (35 mW) non-dispersive infrared (NDIR) CO2 gas sensor using thin film multilayer optical filters. Current sensor spectral response, spans 2500 nm–5000 nm via use of a pentanary alloy LED/photodiode optopair grown by molecular beam epitaxy (MBE), resulting in sensor sensitivity to gases with absorption bands in this region, including N2O. To reduce the effective spectral response of the sensor, capturing only CO2, a multilayer thin film optical interference bandpass filter has been designed and deposited directly onto the diode epi-structures using microwave plasma assisted DC magnetron sputtering. Three different coating configurations have been explored; LED-only coated, photodiode only coated and both coated. Gas sensor response to N2O for each coating configuration has been explored. It was found that application of an optical bandpass filter onto both the sensor LED and photodiode only was the most effective method of reducing sensor response to N2O, however no signal was observed in one of the two “LED and PD coated”, therefore optimal coating configuration for cross-talk reduction is subject to further investigation.",
keywords = "CO2 sensor, thin films, mid-IR, microwave-assisted DC magnetron sputtering, multilayer optical interference filter, mid infrared light emitting diodes, mid infrared photodiodes, capnography, surgical anaesthesia, nitrous oxide, cross-talk, breath analysis",
author = "Lewis Fleming and Des Gibson and Shigeng Song and Cheng Li and Stuart Reid",
year = "2018",
month = "2",
day = "25",
doi = "10.1016/j.surfcoat.2017.09.033",
language = "English",
volume = "336",
pages = "9--16",
journal = "Surface & Coatings Technology",
issn = "0257-8972",
publisher = "Elsevier B.V.",

}

TY - JOUR

T1 - Reducing N2O induced cross-talk in a NDIR CO2 gas sensor for breath analysis using multilayer thin film optical interference coatings

AU - Fleming, Lewis

AU - Gibson, Des

AU - Song, Shigeng

AU - Li, Cheng

AU - Reid, Stuart

PY - 2018/2/25

Y1 - 2018/2/25

N2 - Carbon dioxide (CO2) gas sensing is an important aspect in the biomedical field of capnography, where cheap, fast and accurate measurement of exhaled CO2 vs. time is crucial in the evaluation of lung and tracheal function during surgical anaesthesia and is an under-used bio-marker for underlying respiratory conditions. Current detection methods do not adequately meet these requirements and suffer from considerable cross-talk associated with the commonly used anaesthetic gas nitrous oxide (N2O). In this work, we report how cross-talk can be reduced in a commercially available, low power (35 mW) non-dispersive infrared (NDIR) CO2 gas sensor using thin film multilayer optical filters. Current sensor spectral response, spans 2500 nm–5000 nm via use of a pentanary alloy LED/photodiode optopair grown by molecular beam epitaxy (MBE), resulting in sensor sensitivity to gases with absorption bands in this region, including N2O. To reduce the effective spectral response of the sensor, capturing only CO2, a multilayer thin film optical interference bandpass filter has been designed and deposited directly onto the diode epi-structures using microwave plasma assisted DC magnetron sputtering. Three different coating configurations have been explored; LED-only coated, photodiode only coated and both coated. Gas sensor response to N2O for each coating configuration has been explored. It was found that application of an optical bandpass filter onto both the sensor LED and photodiode only was the most effective method of reducing sensor response to N2O, however no signal was observed in one of the two “LED and PD coated”, therefore optimal coating configuration for cross-talk reduction is subject to further investigation.

AB - Carbon dioxide (CO2) gas sensing is an important aspect in the biomedical field of capnography, where cheap, fast and accurate measurement of exhaled CO2 vs. time is crucial in the evaluation of lung and tracheal function during surgical anaesthesia and is an under-used bio-marker for underlying respiratory conditions. Current detection methods do not adequately meet these requirements and suffer from considerable cross-talk associated with the commonly used anaesthetic gas nitrous oxide (N2O). In this work, we report how cross-talk can be reduced in a commercially available, low power (35 mW) non-dispersive infrared (NDIR) CO2 gas sensor using thin film multilayer optical filters. Current sensor spectral response, spans 2500 nm–5000 nm via use of a pentanary alloy LED/photodiode optopair grown by molecular beam epitaxy (MBE), resulting in sensor sensitivity to gases with absorption bands in this region, including N2O. To reduce the effective spectral response of the sensor, capturing only CO2, a multilayer thin film optical interference bandpass filter has been designed and deposited directly onto the diode epi-structures using microwave plasma assisted DC magnetron sputtering. Three different coating configurations have been explored; LED-only coated, photodiode only coated and both coated. Gas sensor response to N2O for each coating configuration has been explored. It was found that application of an optical bandpass filter onto both the sensor LED and photodiode only was the most effective method of reducing sensor response to N2O, however no signal was observed in one of the two “LED and PD coated”, therefore optimal coating configuration for cross-talk reduction is subject to further investigation.

KW - CO2 sensor

KW - thin films

KW - mid-IR

KW - microwave-assisted DC magnetron sputtering

KW - multilayer optical interference filter

KW - mid infrared light emitting diodes

KW - mid infrared photodiodes

KW - capnography

KW - surgical anaesthesia

KW - nitrous oxide

KW - cross-talk

KW - breath analysis

U2 - 10.1016/j.surfcoat.2017.09.033

DO - 10.1016/j.surfcoat.2017.09.033

M3 - Article

VL - 336

SP - 9

EP - 16

JO - Surface & Coatings Technology

JF - Surface & Coatings Technology

SN - 0257-8972

ER -