Microfluidic Gas Sensors: Detection Principle and Applications

Abstract

With the rapid growth of emerging point-of-use (POU)/point-of-care (POC) detection technologies, miniaturized sensors for the real-time detection of gases and airborne pathogens have become essential to fight pollution, emerging contaminants, and pandemics. However, the low-cost development of miniaturized gas sensors without compromising selectivity, sensitivity, and response time remains challenging. Microfluidics is a promising technology that has been exploited for decades to overcome such limitations, making it an excellent candidate for POU/POC. However, microfluidic-based gas sensors remain a nascent field. In this review, the evolution of microfluidic gas sensors from basic electronic techniques to more advanced optical techniques such as surface-enhanced Raman spectroscopy to detect analytes is documented in detail. This paper focuses on the various detection methodologies used in microfluidic-based devices for detecting gases and airborne pathogens. Non-continuous microfluidic devices such as bubble/droplet-based microfluidics technology that have been employed to detect gases and airborne pathogens are also discussed. The selectivity, sensitivity, advantages/disadvantages vis-a-vis response time, and fabrication costs for all the microfluidic sensors are tabulated. The microfluidic sensors are grouped based on the target moiety, such as air pollutants such as carbon monoxide and nitrogen oxides, and airborne pathogens such as E. coli and SARS-CoV-2. The possible application scenarios for the various microfluidic devices are critically examined.

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“…However, compared with the SERS/Raman SEC, the employment of UV-Vis SEC in microfluidics is more used, which is probably because the electrode substrate can be more easily prepared. As shown in Figure 10 (a1–a3), in this interesting work reported by Colina et al, one easy method to employ or transfer commercial SWCNTs to different nonconductor and transparent supports as the WE is reported [ 174 ]. This work removes the often-employed hydraulic press step from the WE preparation process, significantly expanding the possibility of transferring the SWCNT film to almost any support.…”

“… ( a1 ) a Photograph of the assembled cell ready to measure, ( a2 ) a schematic view of the disassembled cell, and ( a3 ) a detailed schematic view of the experimental setup. Reprinted from [ 174 ], with permission from ACS Publications. ( b ) Illustration of the microfluidic setup for UV-Vis SEC measurements.…”

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