A wireless, remote query magnetoelastic CO2 sensor

This paper presents a wireless, passive, remote query CO2 sensor comprising a ribbon-like magnetoelastic thick-film coated with a mass-changing CO2 re sponsive polymer synthesized from acrylamide and isooctylacrylate. In respo nse to a magnetic held impulse, the magnetostrictive magnetoelastic sensor vibrates at a characteristic resonant frequency that is inversely dependent upon the mass of the attached CO2 responsive polymer. The mechanical vibra tions of the magnetostrictive sensor launch magnetic flux, which can be det ected remotely using a pickup coil. By monitoring the resonant frequency of the passive sensor, the atmospheric CO2 concentration can be determined wi thout the need for physical connections to the sensor or specific alignment requirements. The effect of humidity and the CO2 responsive copolymer comp osition on the measurement sensitivity are reported. Greatest sensitivity i s achieved with a polymer comprising a 1:1 mole ratio of acrylamide to isoo ctyl acrylate. A 0.7% change in atmospheric CO2 concentration can be detect ed for a 20 mum thick polymer coated sensor.