This project focuses on validating and developing prototypes derived from the research carried out in the subproject PID2020-118410RB-C22, which belongs to a coordinated one entitled “Electro-acoustic devices for upcoming sub-6GHz 5G applications (EAD5G)”, ending in August 2024. Under this subproject we are developing and applying microelectronic materials to the fabrication of Thin Film Electroacoustic Resonators, more specifically Solidly Mounted Resonators (SMR), which can be used as gravimetric gas sensors. These devices belong to the Micro-Electro-Mechanical Systems (MEMS) family and show high performance as gravimetric sensors working in the GHz range. They offer advantages such as miniaturization, low fabrication costs, high resolution, their integrated circuits (IC) capability and the possibility of being implemented in array configurations. In addition, they can work in harsh environments, specifically at high temperatures. We have successfully developed and optimized materials for the SMR proper operation at high frequencies and high temperatures and started testing these devices as high temperature NOx sensors. One of the pursued applications is the automotive sector, where a variety of sensors, and, more specifically, MEMS-based sensors are highly demanded. The automotive sector is within the driven and most economically relevant sectors in Spain. The production of vehicles has shown an increase in 15% only from the beginning of 2023 and is expected to continue growing. With the increased vehicles production there is also a demand for safer environments within the cities. Monitoring the exhaust contaminating gases of these vehicles has become pivotal to keep the air quality in the cities optimal. SMR-MEMS operating at high temperatures and high frequencies are proving to be ideal candidates as they can detect different harmful gases and boost the vehicles IoT integration considering the actual 5G network.
So far different sensor prototypes have been tested under different gas environments, being able to detect VOCs like toluene and NOx compounds by applying different functional layers. Specific ad-hoc readout systems are under development.