A PASSIVE WIRELESS GAS SENSOR BASED ON MICROSTRIP ANTENNA WITH COPPER NANORODS

Abstract

Applications of copper (Cu) nanorod arrays, produced by glancing angle deposition (GLAD) technique, which extends the function of conventional microstrip antennas to encompass passive wireless gas sensors at microwave frequencies are presented. The proposed microstrip antenna consists of Cu nanorod arrays grown on silicon wafers which were coated with thin fllms of Cu of 50nm in thickness. To study the efiect of the length of Cu nanorods on antenna performance, Cu nanorods of difierent lengths (400, 700, and 1000nm) were fabricated. The efiects of Cu nanorods morphologies (Cu thin fllm, closely-spaced Cu nanorods, and well-separated Cu nanorods), were investigated too. Conventional microstrip antennas based on sputtered Cu thin fllm were prepared for comparison. It was found that as the length of Cu nanorods increases, the antennas exhibit a wider bandwidth and lower frequency resonance than those of the conventional antennas based on Cu thin fllm. Furthermore, moving from ∞at surface to well-separated nanorods results in a decrease in the resonant frequency, while there was no observable efiect on the bandwidth. These enhancements are attributed to the mutual coupling occurring among Cu nanorods. Based on the antenna characterization, the 1000nm long Cu nanorods sample was selected for gas detection measurements due to its observed sharp resonance and narrow bandwidth. The detection mechanism is based on the change of in the magnitude of the re∞ection coe-cient as well as the resonant frequency due to the introductions of difierent gases. The proposed sensor based on Cu nanorods shows a signiflcant response in