Selective quantitation of vapors and their mixtures using individual passive multivariable RFID sensors

We demonstrate passive (battery-free) radio frequency identification (RFID) devices for selective and sensitive chemical vapor sensing in the presence of ambient interfering gases. We developed two approaches for RFID sensing (1) when a sensing material is applied onto the resonant antenna to alter its impedance response and (2) when a complementary sensor is attached across an antenna and an integrated circuit (IC) memory chip to alter the impedance response of the sensor. In both approaches, these RFID sensors combine several measured parameters of impedance response with the multivariate analysis of these parameters. Thus, these individual sensors provide a unique capability of multiparameter sensing and rejection of environmental interferences. Sensitivity of developed RFID sensors provides detection of vapors at part-per-billion and part-per-million concentrations. Selectivity of developed RFID sensors facilitates selective quantitation of different individual vapors and their mixtures with a single sensor. Our passive RFID sensors were interrogated by the sensor reader at distances ranging from 0 to 33 cm and demonstrated their reliable operation even at the largest tested distance. In our sensing implementations, not the sensor but the sensor reader provides a 16-bit resolution and high signal-to-noise of the acquired signal. Rejection of interferences with a single sensor and the independence from costly proprietary RFID memory chips that have an analog input promise to impact numerous sensing applications.