Carbon dioxide gas sensors have been fabricated by self-assembling single-wall nanotube films on a surface acoustic wave delay line operating at 286 MHz. Polymer functionalization was used to enhance the sensitivity of the carbon nanotubes to carbon dioxide. A pulse radar-type interrogation system was used to monitor the conductivity of the nanotube film by measuring the attenuation of the surface acoustic wave due to film-conductivity changes. The conductivity of the film was found to decrease with carbon dioxide concentration. The effect of varying the sheet conductivity of the nanotube film was examined. Both analytical and experimental results show that controlling the conductivity of the CNT film within a specific range highly enhances the sensitivity to carbon dioxide. Experimental results show that the sensor tracks carbon dioxide concentration changes between 0% and 10%. The final sensor is sensitive, small and wirelessly interrogable, thus making it potentially useful for respiratory monitoring.
Bibliographical noteFunding Information:
The authors thank Dr. Xun Yu for guidance on nanotube film preparation and Dr. Serdar Sezen for helping with micro-fabricating SAW delay lines. One of the authors was funded by the NSF REU program during the summer of 2006.
- Carbon dioxide
- Carbon nanotubes
- Gas sensing
- Surface acoustic wave sensors