Intelligent Mobile Electronic Nose System Comprising a Hybrid Polymer-Functionalized Quartz Crystal Microbalance Sensor Array

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.

Room-temperature ppb-level trimethylamine gas sensors functionalized with citric acid-doped polyvinyl acetate nanofibrous mats

“…[11][12][13][14][15][16][17] The resonance frequency of the crystal shifts to a a Department of Materials Engineering, Institut Teknologi Sumatera, Terusan lower value when the target analytes are adsorbed on the sensor surface. 18,19 QCM transducers can be functionalized using a variety of coating materials with high sensitivity and selectivity. 10,20 The QCM-based TMA sensors incorporating different sensing materials (polymers [21][22][23][24] and metal oxides [25][26][27] ) have been well studied, where they are preferably formed as nanostructures to enhance their specific-surfacearea-to-volume ratios.…”

Fast and noninvasive electronic nose for sniffing out COVID-19 based on exhaled breath-print recognition

“…67,68 There, the surfaces of semiconductor nanostructures were often functionalized with certain self-assembled monolayers (SAMs) or polymers to detect the target gas molecules speci cally. 33,35,69 Nevertheless, those organic materials suffer from low robustness. They are all wellknown to degrade within a short duration of use (i.e., their chemical compositions will alter downgrading the sensor performance).…”

“…Depending on their working principles and materials, several thin-lm and micro-/nanoscale gas sensors can be employed as main detecting components in the electronic nose, which include gravimetric sensors (e.g., surface acoustic wave resonators, resonant micro-/nanocantilevers, and quartz crystal microbalances) [32][33][34][35][36][37][38][39] , chemoresistive sensors (e.g., metal oxide semiconductor, polymer, two-dimensional material, and carbon-based sensors) [40][41][42][43] , colorimetric sensors (e.g., printable pastes and optical dyefunctionalized washable threads) 44,45 , and optical sensors (e.g., visible and infrared micro-/nanoLEDs) [46][47][48][49] . Among them, chemoresistive metal oxide semiconductor gas sensors have been favorable, especially for VOC detection, due to their excellent characteristics (i.e., low cost, short response time, simple measurement setup, high durability, and long lifetime).…”

Portable Tools for COVID-19 Point-of-Care Detection: A Review

“…Accuracy of the COVID-19 biosensors is also commonly assessed using clinical samples by applying methods that are the same as the methods for finding sensitivity and specificity or selectivity. However, the formula used for accuracy calculation is as follows [29], [36], [30], [34]:…”