Simultaneous detection of particles and airflow with a MEMS piezoresistive cantilever

This paper describes a particle and airflow sensor using a MEMS piezoresistive cantilever with the dimensions of 250 μm × 200 μm × 0.29 μm. The sensor structure is simple and detects both the airflow velocity and particle collisions by measuring the fractional resistance change due to the cantilever bending. The signals of the airflow velocity and particle collisions can be simultaneously detected by distinguishing continuous and pulse responses. The sensitivity to the airflow velocity was 1.2 × 10 ^-3 (m/s)^-1 from 0 to 2.5 m s^-1. When a particle of 35 μm diameter (Lycopodium) collided with the cantilever surface, the fractional resistance change varied with the collision. After the collision, reverberation occurred at 3 kHz, which was the same as the resonance frequency of the cantilever. The magnitude of the fractional resistance changes due to particle collision was proportional to the airflow velocity. The sensitivity to particle collision was 2.0 × 10^-3 (m/s)^-1 when the airflow velocity varied between 0 and 2.5 m s^-1.