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Carbon-nanotube loaded antenna-based ammonia gas sensor

Research output: Contribution to journalArticleScientificpeer-review


Original languageEnglish
Article number6016223
Pages (from-to)2665-2673
Number of pages9
JournalIEEE Transactions on Microwave Theory and Techniques
Issue number10 PART 2
Publication statusPublished - 2011
Publication typeA1 Journal article-refereed


Carbon nanotubes (CNTs) have been researched extensively for gas-sensing applications due to their unique electrical, chemical, and structural properties. Single-walled carbon nanotubes (SWNTs) have been predominantly used due to their superior electrical conductivity and higher sensitivity relative to multiwalled CNTs. This paper presents the design and characterization of a novel planar sensor fabricated on paper substrate to detect small concentrations of ammonia gas, using the shift in resonance frequency of a patch antenna as the discriminator. We have investigated three main design issues in depth. First, functionalization of the SWNTs with a polymer is studied in order to enhance the gas detection sensitivity. Second, a thin film of the functionalized SWNT is characterized to create a surface impedance model for the explanation and prediction of the resonance shift due to different gas concentrations. Finally, as a proof of concept, functionalized SWNTs are integrated into a patch antenna design and the return loss is measured in a closed-system environment to show high sensitivity for low concentrations of ammonia gas. The proposed antenna-based wireless gas sensor can be utilized in several applications, given its small form factor, light weight, and little to no power requirements.


  • Carbon nanotubes (CNTs), Gas sensors, Inkjet printing, Passive detection, Poly(m-aminobenzene sulfonic acid) single-walled carbon nanotube (PABS-SWNT), Power scavenging, Wireless sensor node