In this study, we present a novel reusable surface acoustic wave (SAW)-based particulate matter (PM) sensor system capable of simultaneously and selectively detecting PM10 and PM2.5. This is the first implementation of an integrated porous microstructure membrane, acting as a mechanical filter for particle separation, combined with an on-board microheater for particle detachment, enabling sensor reusability. The membrane featured holes of approximately 3 µm and 11 µm in diameter, allowing for selective detection of PM2.5 and PM10, respectively. A two-port SAW resonator structure and 128° YX LiNbO₃ substrate was selected for the sensor platform. The microheater was co-fabricated with the SAW sensor to reduce additional processing time and cost. The porous membrane filter was placed over the sensor, covering only the interdigital transducers (IDTs) and reflectors. COMSOL simulations were used to analyze the heater’s thermal performance, particle trajectories, and eventual particle detachment following microheater activation. For experiments, highly sensitive and stable multi-channel interface electronics were developed to monitor real-time frequency shifts. Sensors were tested in a vacuum chamber with manually controlled particle inlet and microheater. Testing was conducted using PM10 and PM2.5 fine dust, and the sensor demonstrated high sensitivity to both PM categories. A detailed calibration study was performed to ensure the system exclusively detects PM10 and PM2.5. After exposing the sensor surface to three different concentrations of PM, the microheater was activated by applying 12 V, allowing the device to reach a maximum temperature of approximately 100 °C. This facilitated the sensor’s recovery to baseline levels under vacuum conditions, making the sensor reusable.
Nawaz et al. (Tue,) studied this question.