VOCs monitoring using differential microwave capacitive resonant transducer and conductive PEDOT:PSS-MWCNTs nanocomposite film for environmental applications

This paper presents the feasibility of a low-cost fully inkjet printed capacitive microwave flexible gas sensor based on a resonant electromagnetic transducer in micro-strip technology with poly (3,4-ethylenedioxythiophene) polystyrene sulfonate and multi wall carbon nanotubes (PEDOT:PSS-MWCNTs) as sensitive material for Volatile Organic Compounds (VOCs) detection. The design and simulation results of the device on paper substrate for differential measurements are first described. This theoretical study based on both analytical and Finite Element Model approaches, validates the operating principle. The fabrication process and experimental devices are then presented, as well as electrical characterization results, both in air and under selected vapor analytes. These experimental results show the good sensor repeatability and sensitivity according to the transmission S parameter resonant frequency shift equal to -2.153 kHz/ppm and -1.855 kHz/ppm for ethanol and toluene vapor concentrations from 500 to 1300 ppm, respectively. This leads to conclude on promising future of such passive sensors and further integration into real-time multi-sensing platform adaptable for the Internet of Things (IoT).