Enhancing sensitivity using frequency localization factor in gas sensor based antisymmetric weakly coupled resonators

This study presents an antisymmetric weakly coupled aluminum nitride (AIN)-piezoelectric MEMS gas sensor for nitrogen concentration detection in helium. The sensor's design uses mechanically weakly coupled bridge and cantilever resonators to monitor changes in surrounding gas thermal conductivity. The impact of varying electrothermal voltage on system dynamics was investigated, demonstrating a first global mode with no frequency variation and a second global mode with significant variation. Two modes veering phenomena were identified at distinct voltages. To quantify the system's sensitivity to nitrogen concentration in helium, the dimensionless function, Frequency Localization Factor, was introduced. The sensing performance for increasing nitrogen concentration, measured experimentally, shows high sensitivity and good linearity with low power consumption, making it suitable for applications of Internet of Things and wireless sensor networks.