Disposable, paper-based, inkjet-printed humidity and H2S gas sensor for passive sensing applications
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Abdul Quddious, et al., " Disposable, paper-based, inkjet-printed humidity and H2S gas sensor for passive sensing applications" . Sensors, 16 (12), 2016, 2073.
An inkjet-printed, fully passive sensor capable of either humidity or gas sensing is presented herein. The sensor is composed of an interdigitated electrode, a customized printable gas sensitive ink and a specialized dipole antenna for wireless sensing. The interdigitated electrode printed on a paper substrate provides the base conductivity that varies during the sensing process. Aided by the porous nature of the substrate, a change in relative humidity from 18% to 88% decreases the electrode resistance from a few Mega-ohms to the kilo-ohm range. For gas sensing, an additional copper acetate-based customized ink is printed on top of the electrode, which, upon reaction with hydrogen sulphide gas (H 2 S) changes, both the optical and the electrical properties of the electrode. A fast response time of 3 min is achieved at room temperature for a H 2 S concentration of 10 ppm at a relative humidity (RH) of 45%. The passive wireless sensing is enabled through an antenna in which the inner loop takes care of conductivity changes in the 4–5 GHz band, whereas the outer-dipole arm is used for chipless identification in the 2–3 GHz band.