{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,26]],"date-time":"2026-09-26T10:24:58Z","timestamp":1790418298764,"version":"4.1.0"},"reference-count":42,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2020,7,10]],"date-time":"2020-07-10T00:00:00Z","timestamp":1594339200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100010665","name":"H2020 Marie Sk\u0142odowska-Curie Actions","doi-asserted-by":"publisher","award":["643095"],"award-info":[{"award-number":["643095"]}],"id":[{"id":"10.13039\/100010665","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Micromachines"],"abstract":"<jats:p>Formaldehyde (HCHO), a chemical compound used in the fabrication process of a broad range of household products, is present indoors as an airborne pollutant due to its high volatility caused by its low boiling point (    T = \u2212 19     \u00b0C). Miniaturization of analytical systems towards palm-held devices has the potential to provide more efficient and more sensitive tools for real-time monitoring of this hazardous air pollutant. This work presents the initial steps and results of the prototyping process towards on-chip integration of HCHO sensing, based on the Hantzsch reaction coupled to the fluorescence optical sensing methodology. This challenge was divided into two individually addressed problems: (1) efficient airborne HCHO trapping into a microfluidic context and (2) 3,5\u2013diacetyl-1,4-dihydrolutidine (DDL) molecular sensing in low interrogation volumes. Part (2) was addressed in this paper by proposing, fabricating, and testing a fluorescence detection system based on an ultra-low light Complementary metal-oxide-semiconductor (CMOS) image sensor. Two three-layer fluidic cell configurations (quartz\u2013SU-8\u2013quartz and silicon\u2013SU-8\u2013quartz) were tested, with both possessing a 3.5 \u00b5L interrogation volume. Finally, the CMOS-based fluorescence system proved the capability to detect an initial 10 \u00b5g\/L formaldehyde concentration fully derivatized into DDL for both the quartz and silicon fluidic cells, but with a higher signal-to-noise ratio (SNR) for the silicon fluidic cell (    S N  R  s i l i c o n   = 6.1    ) when compared to the quartz fluidic cell (    S N  R  q u a r t z   = 4.9    ). The signal intensity enhancement in the silicon fluidic cell was mainly due to the silicon absorption coefficient at the excitation wavelength,    \u00a0 a  (   \u03bb  a b s   = 420 \u00a0 nm  )  = 5 \u00d7   10  4     \u00a0 cm    \u2212 1      , which is approximately five times higher than the absorption coefficient at the fluorescence emission wavelength,     a  (   \u03bb  e m   = 515 \u00a0 nm  )  = 9.25 \u00d7   10  3     \u00a0 cm    \u2212 1      .<\/jats:p>","DOI":"10.3390\/mi11070673","type":"journal-article","created":{"date-parts":[[2020,7,10]],"date-time":"2020-07-10T09:25:28Z","timestamp":1594373128000},"page":"673","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["Optofluidic Formaldehyde Sensing: Towards On-Chip Integration"],"prefix":"10.3390","volume":"11","author":[{"given":"Daniel","family":"Mariuta","sequence":"first","affiliation":[{"name":"Institute of Microstructure Technology, Campus Nord, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany"},{"name":"Institut Cl\u00e9ment Ader (ICA), Universit\u00e9 de Toulouse, CNRS, INSA, ISAE-SUPAERO, Mines-Albi, UPS, 31400 Toulouse, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Arumugam","family":"Govindaraji","sequence":"additional","affiliation":[{"name":"Institute of Microstructure Technology, Campus Nord, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3434-3848","authenticated-orcid":false,"given":"St\u00e9phane","family":"Colin","sequence":"additional","affiliation":[{"name":"Institut Cl\u00e9ment Ader (ICA), Universit\u00e9 de Toulouse, CNRS, INSA, ISAE-SUPAERO, Mines-Albi, UPS, 31400 Toulouse, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6352-1792","authenticated-orcid":false,"given":"Christine","family":"Barrot","sequence":"additional","affiliation":[{"name":"Institut Cl\u00e9ment Ader (ICA), Universit\u00e9 de Toulouse, CNRS, INSA, ISAE-SUPAERO, Mines-Albi, UPS, 31400 Toulouse, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"St\u00e9phane","family":"Le Calv\u00e9","sequence":"additional","affiliation":[{"name":"Universit\u00e9 de Strasbourg, CNRS, ICPEES UMR 7515, F-67000 Strasbourg, France"},{"name":"In\u2019Air Solutions, 25 rue Becquerel, 67000 Strasbourg, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4354-7295","authenticated-orcid":false,"given":"Jan G.","family":"Korvink","sequence":"additional","affiliation":[{"name":"Institute of Microstructure Technology, Campus Nord, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7577-4463","authenticated-orcid":false,"given":"Lucien","family":"Baldas","sequence":"additional","affiliation":[{"name":"Institut Cl\u00e9ment Ader (ICA), Universit\u00e9 de Toulouse, CNRS, INSA, ISAE-SUPAERO, Mines-Albi, UPS, 31400 Toulouse, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7018-2338","authenticated-orcid":false,"given":"J\u00fcrgen J.","family":"Brandner","sequence":"additional","affiliation":[{"name":"Institute of Microstructure Technology, Campus Nord, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2020,7,10]]},"reference":[{"key":"ref_1","unstructured":"(2019, December 24). 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