Realizing a Highly Compact Particulate Matter Sensor With a MEMS-Based Resonant Membrane

With increasing air pollution levels across the globe, there has been a significant increase in the global health crisis. But the problem remains unchecked in various parts of the world, due to the lack of low-cost and high accuracy air quality sensors. This paper proposes a new technique based on piezoelectric micro-electro-mechanical systems (MEMS) to measure the amount of particulate matter (PM) suspended in the air. Commercially available PM sensors suffer from many disadvantages - namely size, cost, and accuracy. Previous attempts at using MEMS to measure PM have failed to make a significant impact due to the lack of a mechanism to sort the suspended particles based on their sizes and clear the sensing area from the particles after each measurement. The sensor proposed here, consisting of i) a piezoelectric resonating membrane, ii) a virtual impactor, and iii) a thermophoretic plate attempts to address the issues faced by other sensors, while achieving a very compact size and a significantly lower cost. On exposing the sensor to suspended particles in a container, a significant shift in the resonant frequency is observed, once the particles settle on the resonating membrane. The gradual shift in the resonant frequency supports the application of the proposed sensing solution to measure the mass of the PM in the air.