Abstract
We devised a low-cost mobile electronic nose (e-nose) system using a quartz crystal microbalance (QCM) sensor array functionalized with various polymer-based thin active films (i.e., polyacrylonitrile, poly(vinylidene fluoride), poly(vinyl pyrrolidone), and poly(vinyl acetate)). It works based on the gravimetric detection principle, where the additional mass of the adsorbed molecules on the polymer surface can induce QCM resonance frequency shifts. To collect and process the obtained sensing data sets, a multichannel data acquisition (DAQ) circuitry was developed and calibrated using a function generator resulting in a device frequency resolution of 0.5 Hz. Four prepared QCM sensors demonstrated various sensitivity levels with high reproducibility and consistency under exposure to seven different volatile organic compounds (VOCs). Moreover, two types of machine learning algorithms (i.e., linear discriminant analysis and support vector machine models) were employed to differentiate and classify those tested analytes, in which classification accuracies of up to 98 and 99% could be obtained, respectively. This high-performance e-nose system is expected to be used as a versatile sensing platform for performing reliable qualitative and quantitative analyses in complex gaseous mixtures containing numerous VOCs for early disease diagnosis and environmental quality monitoring.
Highlights
Electronic nose (e-nose) technology has been developed by scientists worldwide and greatly used in many application fields by mimicking and advancing the olfactory function of human beings,[1] e.g., in medical care for noninvasive early disease diagnosis,[2−4] food industry for product quality assurance,[5−8] environmental monitoring for continuously online/in situ hazardous gas detection,[9] and agriculture for plant protection[10−12] via monitoring and classification of volatile organic compounds (VOCs)
Due to their broad selectivity and availability, commercial gas sensors based on metal-oxide semiconductors (MOSs) have often been utilized by many researchers as the main part of the e-nose sensor array.[13−15] these sensors consume relatively high power as they need to be activated at high temperatures during operation, limiting their implementation in a portable system
Low-power microlight plates have been developed using gallium nitride (GaN) light-emitting diode (LED) technology as photoactivated micropower gas sensors,[18] where they could result in microwatt-range power consumption when combined with zinc oxide (ZnO) nanoparticles as an active material for selective NO2 monitoring.[19,20]
Summary
Electronic nose (e-nose) technology has been developed by scientists worldwide and greatly used in many application fields by mimicking and advancing the olfactory function of human beings,[1] e.g., in medical care for noninvasive early disease diagnosis,[2−4] food industry for product quality assurance,[5−8] environmental monitoring for continuously online/in situ hazardous gas detection,[9] and agriculture for plant protection[10−12] via monitoring and classification of volatile organic compounds (VOCs). An e-nose system consists normally of some or many gas sensors that are assembled into an array targeting different analytes, a so-called sensor array Due to their broad selectivity and availability, commercial gas sensors based on metal-oxide semiconductors (MOSs) have often been utilized by many researchers as the main part of the e-nose sensor array.[13−15] these sensors consume relatively high power (few hundreds of milliwatt) as they need to be activated at high temperatures during operation, limiting their implementation in a portable system. They are normally sealed in a fixed housing. Highly selective and sensitive gas detectors with low power consumption, easy surface modification, and low fabrication costs are still demanded by sensor communities to be integrated into the e-nose system
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