Thin-film based passive RFID sensor tag for detection of packaged food volatiles
Abstract In this paper, a near-field wireless thin-film coated RFID compatible sensor tag is presented for profiling packaged food volatiles at room temperature. The sensor tag consists of a thin-film coated interdigitated capacitor interrogated in two different configurations: (i) direct-wired configuration, and (ii) wireless configuration. Polyaniline (PANi) is chosen as the thin film to be coated on the interdigitated capacitor due to its specificity towards packaged food, detection of Ammonia. The sensitivity of the sensor is characterized at room temperature and at atmospheric pressure. In the direct-wired configuration, different concentration of Ammonia gas is introduced into an enclosed chamber and the conductivity across the film is measured. In the wireless configuration, an inductor is soldered across the interdigitated capacitor to form an inductor-capacitor (LC) resonant tank. The resonance frequency is wirelessly interrogated using an external pick-up coil (reader coil) and the frequency shift is monitored. The proposed sensor can detect as low as 3 ppm of Ammonia making it a highly sensitive sensor, and it can be easily adapted to monitor packaged food quality across the supply chain.