Fully Inkjet-Printed Gas-Sensing Antenna Based on Carbon Nanotubes for Wireless Communication Applications

Abstract This study presents a fully inkjet-printed antenna based on carbon nanotubes (CNTs) for ammonia-gas-sensing. The antenna-embedded CNT film must satisfy strict requirements in terms of resistance, uniformity, and stability. Various resistive-type gas sensors based on CNTs, which are controlled by droplet spacing (DS) and multiple passes, are realized by inkjet-printing technology to investigate their sensing characteristics. The gas response decreases with increasing CNT density; however, the distribution of repeatability is tighter because the connection junctions among CNTs increase and the conductive paths saturate. The relationship between CNT density and gas-sensing response is presented for the first time. According to the response of the resistive-type gas sensors, low resistance and stable sensing response of a DS = 20 m and 20-pass CNT film is suitable for embedding into an antenna for gas-sensing. The sensitivities of insertion and return losses under exposure to NH3 of the gas-sensing antenna demonstrate a linear relationship and reproducibility. The gas-sensing antenna based on CNT films exhibits two-dimensional value responses, real-time gas detection, reproducibility, and reversibility, which provide a viable option for wireless sensing systems.