Passive wireless gas sensors based on the LTCC technique

Many of the existing gas sensors cannot offer long-term continuous performance, rendering them selected ineffective for environmental and point-of-care monitoring tasks. The problem may arise from the limitation in accessible power supplies for their operation and signal communications. As a solution, a wireless passive gas sensor based on low temperature co-fired ceramic (LTCC) technology is presented in this work. The sensor consists of a planar inductor-interdigital capacitor resonant antenna circuit, covered with gas sensitive coatings. The antenna together with this pair of interdigital electrodes was fabricated using the LTCC process. Gas sensitive films were made of two dimensional tin disulfide (SnS₂) nanostructures, which were deposited on the interdigital electrodes by drop-casting method. The gas sensing performance was investigated by monitoring the impedance phase angle changes of the antenna in response to different gas types and concentrations.