Nanowire sensor applications based on radio frequency phase shift in coplanar waveguide

This paper presents the design and,development of a gas sensor based on phase monitoring of reflected waves at radio frequencies for various dichloromethane vapors. Composite thin film with fanctionalized carbon nanotubes (f-CNT) and polymethylmethacrylate (PMMA) was employed as a sensing material on a coplanar waveguide and its impedance was monitored for various concentrations. Conductivity change of the composite due to absorption of dichloromethane vapors was clearly observed by resistance measurements. When the f-CNTs/PMMA composite is exposed to dichloromethane with low vapor concentration, phase monitoring of reflected waves from resistive load exhibited higher sensitivity than resistance measurements. With high sensitivity at radio frequency, a wireless gas sensing network integrated-with power divider and antenna is introduced.