A RFID-based wireless NH3 gas detector using spin coated carbon nanotubes as sensitive layer

A radio frequency identification (RFID)-based wireless ammonia (NH3) gas detector was developed to work at 868 MHz. Using carbon nanotubes (CNT) thin film as a sensitive layer, a standard RFID tag is transformed into an RFID gas detector. First, RFID copper antenna on flexible polyethylene terephthalate (PET) substrate was fabricated by combining inkjet printing and copper electroplating. After that, CNT thin film was deposited on RFID antenna by spin coating method. RFID chip AK3 tagsys loop was attached with RFID antenna to form RFID tag. Performance of this gas detector was tested by measuring impedance of the RFID antenna and read-range of the RFID tag before and after being submitted to NH3 gas. The impedance of CNT thin film changed in presence of ammonia, leading to a decrease of the RFID tag read-range. A low-cost passive RFID gas detector is demonstrated with good response to NH3 gas down to 10 ppm, the RFID tag read-range was decreased from 2.5 m to 1.9 m. Besides, the impedance of RFID antenna had shown the good change, from 11.70 - j20.70 to 8.56 - j33.45 after being exposed 1 min to NH3 gas. From this result, this wireless gas detector is promising to be applied in real life to detect gas leakage, especially in relatively harsh and non-light-of-sight environments, because of many advantages such as low-cost, wireless and easy to control.