Advances in micro- and nano-scale resonant mass-sensitive gas sensors: Mechanisms, materials, functionalization and applications

Environment and health are two of the main concerns in the 21st century, driving increased demands for personalized monitoring technologies. Among these, micro- and nano- electromechanical systems (M/NEMS)-based resonant gravimetric gas sensors have garnered significant research attention because of their potential for continuous, real-time, and in-site monitoring of air pollutions and breath biomarkers for human disease diagnostics. Resonant gravimetric gas sensors combine mechanics, chemistry, and materials, with challenges in achieving stable, repeatable, and durable sensing performances because of the instability and susceptible feature of the sensing materials. This review provides a comprehensive summary of the state-of-the-art resonant gravimetric gas sensors. The fundamental mechanisms of these sensors, as well as the most commonly used sensing materials and functionalization techniques, are introduced. Recent progress in strategies to enhance the sensor's key performance metrics, such as selectivity, sensitivity, limit of detection, repeatability, and response time, are discussed in detail. Further, we summarize recent advances in the applications of resonant gravimetric gas sensors in environmental pollution detection and healthcare monitoring. Finally, the challenges and perspectives of this type of gas sensor are discussed. This review is helpful for researchers interested in developing resonant gravimetric gas sensors and in tackling the remaining challenges to accelerate the realization of this class of sensors toward practical applications.