  This paper investigates the performance of the micro-electro-mechanical
systems resonant sensor used for particle detection and concentration
measurement. These fine and ultra-fine particles such as particulate matter
(PM), ferrous particles, and nanoparticles are known to contaminate the
atmosphere, fluids used in industrial machines, and food, respectively. The
physical principles involved in the target particles accumulating on the sensor
are presented. Micro-gravimetric resonators that use piezoelectric and
thermally actuated transducers for particle detection and concentration
measurement in air and high-viscosity liquids are analyzed. Critical sensor
features, such as maximum possible parametric sensitivity, the detection limit
of particle size and mass concentration, linear dynamic range, and output
stability, are thoroughly evaluated.
