A passive wireless CO2 sensing system based on surface acoustic wave technology and carbon nanotube nanocomposite was developed. The gas response of the nanocomposite was about 10% resistance increase under pure CO2. The sensor frequency change was around 0.03% for pure CO2. With paralyne packaging, the sensor frequency change from relative humidity of 0% to 100% at room temperature decreased from over 0.1% to less than 0.01%. The lowest detection limit of the sensor is 1% gas concentration, with 0.0036% frequency change. Wireless module was tested and showed over one foot transmission distance at preferred parallel orientation.
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