{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,14]],"date-time":"2026-03-14T01:20:53Z","timestamp":1773451253965,"version":"3.50.1"},"reference-count":35,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2024,1,11]],"date-time":"2024-01-11T00:00:00Z","timestamp":1704931200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Fraunhofer Internal Programs","award":["Anti-Corona 018-601215"],"award-info":[{"award-number":["Anti-Corona 018-601215"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>A photoacoustic sensor system (PAS) intended for carbon dioxide (CO2) blood gas detection is presented. The development focuses on a photoacoustic (PA) sensor based on the so-called two-chamber principle, i.e., comprising a measuring cell and a detection chamber. The aim is the reliable continuous monitoring of transcutaneous CO2 values, which is very important, for example, in intensive care unit patient monitoring. An infrared light-emitting diode (LED) with an emission peak wavelength at 4.3 \u00b5m was used as a light source. A micro-electro-mechanical system (MEMS) microphone and the target gas CO2 are inside a hermetically sealed detection chamber for selective target gas detection. Based on conducted simulations and measurement results in a laboratory setup, a miniaturized PA CO2 sensor with an absorption path length of 2.0 mm and a diameter of 3.0 mm was developed for the investigation of cross-sensitivities, detection limit, and signal stability and was compared to a commercial infrared CO2 sensor with a similar measurement range. The achieved detection limit of the presented PA CO2 sensor during laboratory tests is 1 vol. % CO2. Compared to the commercial sensor, our PA sensor showed less influences of humidity and oxygen on the detected signal and a faster response and recovery time. Finally, the developed sensor system was fixed to the skin of a test person, and an arterialization time of 181 min could be determined.<\/jats:p>","DOI":"10.3390\/s24020457","type":"journal-article","created":{"date-parts":[[2024,1,11]],"date-time":"2024-01-11T06:52:14Z","timestamp":1704955934000},"page":"457","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":12,"title":["Towards a Miniaturized Photoacoustic Sensor for Transcutaneous CO2 Monitoring"],"prefix":"10.3390","volume":"24","author":[{"given":"Mahmoud","family":"El-Safoury","sequence":"first","affiliation":[{"name":"Fraunhofer Institute for Physical Measurement Techniques IPM, 79110 Freiburg im Breisgau, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Christian","family":"Weber","sequence":"additional","affiliation":[{"name":"Fraunhofer Institute for Physical Measurement Techniques IPM, 79110 Freiburg im Breisgau, Germany"},{"name":"Department of Microsystems Engineering\u2013Institut f\u00fcr Mikrosystemtechnik (IMTEK), University of Freiburg, 79110 Freiburg im Breisgau, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hassan","family":"Yassine","sequence":"additional","affiliation":[{"name":"Department of Microsystems Engineering\u2013Institut f\u00fcr Mikrosystemtechnik (IMTEK), University of Freiburg, 79110 Freiburg im Breisgau, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"J\u00fcrgen","family":"W\u00f6llenstein","sequence":"additional","affiliation":[{"name":"Fraunhofer Institute for Physical Measurement Techniques IPM, 79110 Freiburg im Breisgau, Germany"},{"name":"Department of Microsystems Engineering\u2013Institut f\u00fcr Mikrosystemtechnik (IMTEK), University of Freiburg, 79110 Freiburg im Breisgau, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4646-8990","authenticated-orcid":false,"given":"Katrin","family":"Schmitt","sequence":"additional","affiliation":[{"name":"Fraunhofer Institute for Physical Measurement Techniques IPM, 79110 Freiburg im Breisgau, Germany"},{"name":"Department of Microsystems Engineering\u2013Institut f\u00fcr Mikrosystemtechnik (IMTEK), University of Freiburg, 79110 Freiburg im Breisgau, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2024,1,11]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"104","DOI":"10.1186\/s13054-020-2776-z","article-title":"Physiology of the Respiratory Drive in ICU Patients: Implications for Diagnosis and Treatment","volume":"24","author":"Jonkman","year":"2020","journal-title":"Crit. 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