A novel highly-sensitive antenna-based “smart skin” gas sensor utilizing carbon nanotubes and inkjet printing

Carbon nanotubes (CNTs) have attractive features for implementation in wireless sensor nodes due to their small size, light weight and low power requirements, and their ability to be functionalized with conductive polymers for the electronic detection of a range of chemical and biological agents. In this paper, we present a single-walled CNT sensor for gas detection that is printed on paper substrate and integrated with a co-planar RF antenna for potential application as a light-weight wireless sensor node. The CNT thin-film loads the antenna and changes its resonant frequency upon exposure to the gas, the resonant frequency shift then being used as a discriminator for the gas detection in trace quantities. Measurements of a CNT-based sensor when exposed to low levels of ammonia reveal a resonance frequency shift of 300 MHz for a patch antenna centered around 6 GHz. To the authors´ knowledge, this is the highest frequency shift reported in literature.