RFID Passive Gas Sensor Integrating Carbon Nanotubes

Abstract

Carbon nanotube (CNT) composites are sensitive to the presence of gases due to their high surface-to-volume ratio and hollow structure that are well suited for gas molecule absorption and storage. Such sensing capability is here integrated with UHF RF identification (RFID) technology to achieve passive and lowcost sensors, remotely readable. CNT film (buckypaper) is used as a localized variable resistive load integrated into a tag antenna, which becomes able to transduce the presence of hazardous gas in the environment, ammonia in this case, into a change of its electromagnetic features. The dynamic range and the hysteresis of the radio sensor are investigated by simulations, equivalent circuits, and articulated experimentations within a true RFID link, providing the proof of concept and some guidelines for tag design.Index Terms-Nanotube, passive gas sensor, RF identification (RFID).

RFID Technology for IoT-Based Personal Healthcare in Smart Spaces

“…Several CIM species have been experimented for applications to RFID sensors, mostly aimed at detecting humidity and ammonia by using carbon nano structures (CNTs), [3] conducting or insulating polymers [4]- [6] and even a simple blotting paper [7].…”

“…Fig. 5 shows the minimum power (estimated by numerical simulations 3 ) that is requested to the UHF RFID reader to activate (turn-on) a small dipole tag implanted, in different positions, into an homogeneous (muscle-like) phantom resembling the human body, interrogated by a 5-dB gain PIFA antenna. Diagrams consider both a well assessed RFID IC (power sensitivity, ) and a better performing chip family (power sensitivity ) that, reasonably, should be available within a couple of years.…”

Passive UHF RFID antennas for sensing applications: Principles, methods, and classifcations

“…A more effective way to retrieve specific sensing data is to provide the tag with a "real" sensor which could be either lumped into a device [37], [38], connected in some part of the tag's antenna (Fig.6b) [39], [40], [41], or instead distributed all over the antenna surface, for instance as a chemical receptor painting [42]. The sensor is hence considered as a lumped or distributed impedance loading Z S (Ψ) on the tag's antenna.…”

“…• b) Loop-driven flat dipole doped with carbon nano structures (CNT), [42] able to sense the presence of ammonia in the environment thanks to the absorbing property of the CNT material deposited between the matching loop and the dipole. Changes in the CNT properties will reflect in mismatch and gain variation, readable through turn-on and backscattered power measurements.…”

Feasibility of Body-Centric Systems Using Passive Textile RFID Tags

“…Nevertheless, there are some emerging applications wherein the variation of the backscattered power is correlated to some physical property of the tag, and, in turn, to the change of the tagged object or of the nearby environment, with the purpose of achieving a sort of RFID passive sensing. This is the case when the tag is coupled to a chemically sensitive substrate detecting the presence of gases, or when the antenna itself is deformed by motion [35].…”