Micromachined Mechanical Resonant Sensors: From Materials, Structural Designs to Applications

Abstract Driving a micro and nanomechanical structure to resonance and observing its resonant motion in the physical world have led to numerous fundamental discoveries in physics, sciences, chemistry, biology, and engineering, as well as device commercialization. Scaling down mechanical structures from micrometric to nanometric size has enabled the utilization of resonant motions to probe material properties and various dynamical phenomena in quantum coherence and squeezing. Recent advances in material sciences and nanofabrication resulted in successful demonstration of ultra‐high frequency operation (GHz range) and ultra‐high quality factor (10 billion) micromachined mechanical resonators (MMRs). The resonant motion of these structures has been utilized as an indispensable tool to weigh biological and chemical species at resolution of atomic mass unit, sense a force as small as zepto‐newton, and to detect numerous other physical parameters. Here, a systematic view on the resonant sensing transduction is provided, underlying physics, and sensing structures realized with micro/nano‐electromechanical systems (MEMS/NEMS) technologies. It is also describe the roles of nanomaterials and structures, nano‐fabrication and rational designs on the resonance frequency and quality factor of MMRs toward high‐performance sensing. This paper discusses the most recent advances in the development of MMRs for material characterization as well as biological, chemical, and physical sensing. Finally, the paper discusses the challenges and perspectives on design, fabrication, and developments of resonant sensors with high quality factor toward quantum sensing, and ultra‐high sensitivity and resolution for classical sensing applications.