RFID tags for wireless electrochemical detection of volatile chemicals

This work outlines a new approach for the construction of a wireless and battery-free broad response vapour sensor. Carbon black/organic polymer composites are known to swell reversibly upon exposure to volatile chemicals. We integrated these types of composites into the electronic elements of a conventional passive RFID tag circuitry to produce resistance changes that result in a change in the RFID tagʹs output signal frequency and amplitude. To identify vapours, arrays of RFID tags with such vapour-sensing elements were constructed, with each tag containing carbon black as the conducting element and a polymer as the sensing element. The different gas–solid partition coefficients for the polymers in the sensor array produce a unique pattern of signal changes that can be used to classify vapours. This sensor array was able to identify and quantify several vapours of interest (water, ammonia, ethanol and toluene).