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

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.