{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,27]],"date-time":"2026-05-27T17:42:06Z","timestamp":1779903726411,"version":"3.53.1"},"reference-count":26,"publisher":"MDPI AG","issue":"16","license":[{"start":{"date-parts":[[2021,8,8]],"date-time":"2021-08-08T00:00:00Z","timestamp":1628380800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100012331","name":"Agentschap Innoveren en Ondernemen","doi-asserted-by":"publisher","award":["160580"],"award-info":[{"award-number":["160580"]}],"id":[{"id":"10.13039\/100012331","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>In this paper, we present a fully integrated Non-dispersive Infrared (NDIR) CO2 sensor implemented on a silicon chip. The sensor is based on an integrating cylinder with access waveguides. A mid-IR LED is used as the optical source, and two mid-IR photodiodes are used as detectors. The fully integrated sensor is formed by wafer bonding of two silicon substrates. The fabricated sensor was evaluated by performing a CO2 concentration measurement, showing a limit of detection of \u223c750 ppm. The cross-sensitivity of the sensor to water vapor was studied both experimentally and numerically. No notable water interference was observed in the experimental characterizations. Numerical simulations showed that the transmission change induced by water vapor absorption is much smaller than the detection limit of the sensor. A qualitative analysis on the long term stability of the sensor revealed that the long term stability of the sensor is subject to the temperature fluctuations in the laboratory. The use of relatively cheap LED and photodiodes bare chips, together with the wafer-level fabrication process of the sensor provides the potential for a low cost, highly miniaturized NDIR CO2 sensor.<\/jats:p>","DOI":"10.3390\/s21165347","type":"journal-article","created":{"date-parts":[[2021,8,8]],"date-time":"2021-08-08T21:35:40Z","timestamp":1628458540000},"page":"5347","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":51,"title":["A Miniaturised, Fully Integrated NDIR CO2 Sensor On-Chip"],"prefix":"10.3390","volume":"21","author":[{"given":"Xiaoning","family":"Jia","sequence":"first","affiliation":[{"name":"Photonics Research Group, INTEC, Ghent University-Imec, Technologiepark 126, 9052 Gent, Belgium"},{"name":"Center for Nano- and Biophotonics, Ghent University, 9000 Gent, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Joris","family":"Roels","sequence":"additional","affiliation":[{"name":"Melexis Technologies NV, Transportstraat 1, 3980 Tessenderlo, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Roel","family":"Baets","sequence":"additional","affiliation":[{"name":"Photonics Research Group, INTEC, Ghent University-Imec, Technologiepark 126, 9052 Gent, Belgium"},{"name":"Center for Nano- and Biophotonics, Ghent University, 9000 Gent, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4667-5092","authenticated-orcid":false,"given":"Gunther","family":"Roelkens","sequence":"additional","affiliation":[{"name":"Photonics Research Group, INTEC, Ghent University-Imec, Technologiepark 126, 9052 Gent, Belgium"},{"name":"Center for Nano- and Biophotonics, Ghent University, 9000 Gent, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2021,8,8]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"7029","DOI":"10.1364\/AO.55.007029","article-title":"Mid-infrared absorption-spectroscopy-based carbon dioxide sensor network in greenhouse agriculture: Development and deployment","volume":"55","author":"Wang","year":"2016","journal-title":"Appl. Opt."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Ortiz Perez, A., Bierer, B., Scholz, L., W\u00f6llenstein, J., and Palzer, S. (2018). A wireless gas sensor network to monitor indoor environmental quality in schools. Sensors, 18.","DOI":"10.3390\/s18124345"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"518","DOI":"10.1002\/1521-3773(20010202)40:3<518::AID-ANIE518>3.0.CO;2-4","article-title":"CO2 technology platform: An important tool for environmental problem solving","volume":"40","author":"Wells","year":"2001","journal-title":"Angew. Chem. Int. Ed."},{"key":"ref_4","unstructured":"Focus, S. (2021, February 13). How Much Does Human Breathing Contribute to Climate Change?. Available online: https:\/\/www.sciencefocus.com\/planet-earth\/how-much-does-human-breathing-contribute-to-climate-change\/."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"691","DOI":"10.1038\/s41893-019-0323-1","article-title":"Direct human health risks of increased atmospheric carbon dioxide","volume":"2","author":"Jacobson","year":"2019","journal-title":"Nat. Sustain."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1422","DOI":"10.1126\/science.abc6197","article-title":"Reducing transmission of SARS-CoV-2","volume":"368","author":"Prather","year":"2020","journal-title":"Science"},{"key":"ref_7","first-page":"2311","article-title":"It is time to address airborne transmission of coronavirus disease 2019 (COVID-19)","volume":"71","author":"Morawska","year":"2020","journal-title":"Clin. Infect. Dis."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"237","DOI":"10.1034\/j.1600-0668.2003.00189.x","article-title":"Risk of indoor airborne infection transmission estimated from carbon dioxide concentration","volume":"13","author":"Rudnick","year":"2003","journal-title":"Indoor Air"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"392","DOI":"10.1021\/acs.estlett.1c00183","article-title":"Exhaled CO2 as COVID-19 infection risk proxy for different indoor environments and activities","volume":"8","author":"Peng","year":"2021","journal-title":"Environ. Sci. Technol. Lett."},{"key":"ref_10","unstructured":"Sage-Emg, U. (2021, August 08). Role of Ventilation in Controlling SARS-CoV-2 Transmission, Available online: https:\/\/assets.publishing.service.gov.uk\/government\/uploads\/system\/uploads\/attachment_data\/file\/928720\/S0789_EMG_Role_of_Ventilation_in_Controlling_SARS-CoV-2_Transmission.pdf."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"9635","DOI":"10.3390\/s120709635","article-title":"A survey on gas sensing technology","volume":"12","author":"Liu","year":"2012","journal-title":"Sensors"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"2537","DOI":"10.1002\/adfm.201500314","article-title":"When Nanoparticles Meet Poly(Ionic Liquid)s: Chemoresistive CO2 Sensing at Room Temperature","volume":"25","author":"Willa","year":"2015","journal-title":"Adv. Funct. Mater."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Boudaden, J., Klumpp, A., Eisele, I., and Kutter, C. (November, January 30). Smart capacitive CO2 sensor. Proceedings of the 2016 IEEE SENSORS, Orlando, FL, USA.","DOI":"10.1109\/ICSENS.2016.7808664"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"012004","DOI":"10.1088\/0957-0233\/24\/1\/012004","article-title":"Optical gas sensing: A review","volume":"24","author":"Hodgkinson","year":"2012","journal-title":"Meas. Sci. Technol."},{"key":"ref_15","unstructured":"Future, M.R. (2021, February 15). Europe Advanced CO2 Sensor Market Analysis\u2014Global Forecast 2016 to 2022. Available online: https:\/\/www.marketresearchfuture.com\/reports\/europe-advanced-co2-sensor-market-2574."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"119","DOI":"10.1016\/j.sna.2019.03.014","article-title":"Highly sensitive photoacoustic gas sensor based on multiple reflections on the cell wall","volume":"290","author":"Chen","year":"2019","journal-title":"Sens. Actuators A Phys."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"4157","DOI":"10.3390\/s130404157","article-title":"Development of an optical gas leak sensor for detecting ethylene, dimethyl ether and methane","volume":"13","author":"Tan","year":"2013","journal-title":"Sensors"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"580","DOI":"10.1016\/j.snb.2013.06.006","article-title":"Non-dispersive infra-red (NDIR) measurement of carbon dioxide at 4.2 \u03bcm in a compact and optically efficient sensor","volume":"186","author":"Hodgkinson","year":"2013","journal-title":"Sens. Actuators B Chem."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"917","DOI":"10.1016\/j.snb.2016.03.081","article-title":"A miniaturized optical gas-composition sensor with integrated sample chamber","volume":"236","author":"Ayerden","year":"2016","journal-title":"Sens. Actuators B Chem."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"21","DOI":"10.1016\/j.snb.2010.11.049","article-title":"Merging ethylene NDIR gas sensors with preconcentrator-devices for sensitivity enhancement","volume":"170","author":"Sklorz","year":"2012","journal-title":"Sens. Actuators B Chem."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Jia, X., Roels, J., Baets, R., and Roelkens, G. (2019). On-chip non-dispersive infrared CO2 sensor based on an integrating cylinder. Sensors, 19.","DOI":"10.3390\/s19194260"},{"key":"ref_22","unstructured":"(2021, March 31). Independent Business Scientific Group (IBSG). Available online: http:\/\/www.ibsg-st-petersburg.com."},{"key":"ref_23","unstructured":"(2021, March 31). MidDOG. Available online: http:\/\/www.mirdog.spb.ru\/products.htm."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"4","DOI":"10.1016\/j.jqsrt.2013.07.002","article-title":"The HITRAN2012 molecular spectroscopic database","volume":"130","author":"Rothman","year":"2013","journal-title":"J. Quant. Spectrosc. Radiat. Transf."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"073302","DOI":"10.1088\/0256-307X\/28\/7\/073302","article-title":"Water vapor interference correction in a non dispersive infrared multi-gas analyzer","volume":"28","author":"Sun","year":"2011","journal-title":"Chin. Phys. Lett."},{"key":"ref_26","unstructured":"Photonics, H. (2021, July 24). Mid Infrared LED, Hamamatsu. Available online: https:\/\/www.hamamatsu.com\/resources\/pdf\/ssd\/l15893_series_etc_kled1085e.pdf."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/16\/5347\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T06:42:26Z","timestamp":1760164946000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/16\/5347"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,8,8]]},"references-count":26,"journal-issue":{"issue":"16","published-online":{"date-parts":[[2021,8]]}},"alternative-id":["s21165347"],"URL":"https:\/\/doi.org\/10.3390\/s21165347","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,8,8]]}}}