title: Disposable, Paper-Based, Inkjet-Printed Humidity and H₂S Gas Sensor for Passive Sensing Applications.
abstract: 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 (H₂S) 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 H₂S 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.
authors.affiliation: Research Institute for Microwave and Millimeterwave Studies (RIMMS), National University of Sciences and Technology (NUST), Islamabad 44000, Pakistan. 12mseeaquddious@seecs.edu.pk.
authors.forename: Abdul
authors.initials: A
authors.lastname: Quddious
authors.affiliation: Computer, Electrical and Mathematical Sciences and Engineering (CEMSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia. shuai.yang@kaust.edu.sa.
authors.forename: Shuai
authors.initials: S
authors.lastname: Yang
authors.affiliation: Research Institute for Microwave and Millimeterwave Studies (RIMMS), National University of Sciences and Technology (NUST), Islamabad 44000, Pakistan. 12mseemmkhan@seecs.edu.pk.
authors.forename: Munawar M
authors.initials: MM
authors.lastname: Khan
authors.affiliation: Research Institute for Microwave and Millimeterwave Studies (RIMMS), National University of Sciences and Technology (NUST), Islamabad 44000, Pakistan. farooq.tahir@seecs.edu.pk.
authors.forename: Farooq A
authors.initials: FA
authors.lastname: Tahir
authors.affiliation: Computer, Electrical and Mathematical Sciences and Engineering (CEMSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia. atif.shamim@kaust.edu.sa.
authors.forename: Atif
authors.initials: A
authors.lastname: Shamim
authors.affiliation: Computer, Electrical and Mathematical Sciences and Engineering (CEMSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia. khaled.salama@kaust.edu.sa.
authors.forename: Khaled N
authors.initials: KN
authors.lastname: Salama
authors.affiliation: Research Institute for Microwave and Millimeterwave Studies (RIMMS), National University of Sciences and Technology (NUST), Islamabad 44000, Pakistan. hammad.cheema@seecs.edu.pk.
authors.forename: Hammad M
authors.initials: HM
authors.lastname: Cheema
keywords: chipless radio frequency identification; gas sensor; hydrogen sulfide gas; inkjet printing; internet-of-things; paper substrate; wireless applications