A wireless, remote query magnetoelastic CO₂ sensor

This paper presents a wireless, passive, remote query CO₂ sensor comprising a ribbon-like magnetoelastic thickfilm coated with a mass-changing CO₂ responsive polymer synthesized from acrylamide and isooctylacrylate. In response to a magnetic field 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 vibrations of the magnetostrictive sensor launch magnetic flux, which can be detected remotely using a pickup coil. By monitoring the resonant frequency of the passive sensor, the atmospheric CO₂ concentration can be determined without the need for physical connections to the sensor or specific alignment requirements. The effect of humidity and the CO₂ responsive copolymer composition on the measurement sensitivity are reported. Greatest sensitivity is achieved with a polymer comprising a 1:1 mole ratio of acrylamide to isooctyl acrylate. A 0.7% change in atmospheric CO₂ concentration can be detected for a 20 μm thick polymer coated sensor.