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Optofluidic Formaldehyde Sensing: Towards On-Chip Integration

Abstract : 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=−19 °C). 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–diacetyl-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–SU-8–quartz and silicon–SU-8–quartz) were tested, with both possessing a 3.5 µL interrogation volume. Finally, the CMOS-based fluorescence system proved the capability to detect an initial 10 µg/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 ( SNRsilicon=6.1 ) when compared to the quartz fluidic cell ( SNRquartz=4.9 ). The signal intensity enhancement in the silicon fluidic cell was mainly due to the silicon absorption coefficient at the excitation wavelength, a(λabs=420 nm)=5×104 cm−1 , which is approximately five times higher than the absorption coefficient at the fluorescence emission wavelength, a(λem=515 nm)=9.25×103 cm−1
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https://hal.archives-ouvertes.fr/hal-02896737
Contributor : Stéphane Colin <>
Submitted on : Wednesday, December 9, 2020 - 6:33:49 PM
Last modification on : Tuesday, July 13, 2021 - 8:20:09 AM
Long-term archiving on: : Wednesday, March 10, 2021 - 7:58:25 PM

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Daniel Mariuta, Arumugam Govindaraji, Stéphane Colin, Christine Barrot, Stéphane Le Calvé, et al.. Optofluidic Formaldehyde Sensing: Towards On-Chip Integration. Micromachines, MDPI, 2020, 11 (7), pp.673. ⟨10.3390/mi11070673⟩. ⟨hal-02896737⟩

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