New Sensor System Integrates Particle Separation and Self-Cleaning for Air Monitoring

Researchers from Ajou University in Suwon, Republic of Korea, have developed a novel sensor system for monitoring airborne particulate matter. The device, described in a study published in Microsystems & Nanoengineering on 24 March 2026, integrates surface acoustic wave (SAW) sensing with porous membranes for particle-size separation and an on-chip microheater for sensor recovery.

This is the first SAW-based particulate matter sensor to integrate a porous microstructure membrane for particle separation with an on-board microheater for particle detachment.

Device Design and Function

The sensor uses two separate sensing channels for different particle size ranges: PM10 and PM2.5. Each channel features a porous filter membrane placed directly above a two-port SAW resonator.

• The PM10 channel uses a membrane with pore diameters of approximately 11 μm.
• The PM2.5 channel uses a membrane with pore diameters of approximately 3 μm.

Simulations and experiments confirmed that the 11 μm membrane allowed both larger and smaller particles to pass, while the 3 μm membrane preferentially passed smaller particles. A key feature is the integrated microheater, which removes accumulated particles by heating, restoring the sensor's baseline and enabling reusability.

Performance and Testing

In controlled laboratory tests, the system demonstrated clear sensitivity to different particle sizes:

• The PM2.5 sensor showed a sensitivity of 0.11 kHz/(μg/m³) to PM2.5 particles.
• The PM10 channel showed a sensitivity of 0.246 kHz/(μg/m³) to PM2.5 particles.
• After a subtraction-based calibration, the PM10 channel showed a sensitivity of 0.218 kHz/(μg/m³) to particles in the 2.5–10 μm size range.

To recover the sensor, the integrated microheater was driven at 12 V, raising the device temperature to approximately 100 °C under vacuum conditions. This self-cleaning process allows the sensor to be reused. Over a five-day testing period, the PM10 channel retained more than 90% of its relative response, and the PM2.5 channel remained above 80%.

Context and Significance

Current techniques for monitoring particulate matter—such as beta-ray absorption, gravimetric methods, and light-scattering—often involve tradeoffs in system size, cost, humidity sensitivity, or reliability. While earlier SAW-based sensors showed high sensitivity, they typically lacked a practical reusable format and clear size selectivity.

By combining particle separation and thermal recovery on a single platform, the system may reduce reliance on external separation components used in some setups.

The researchers conclude that this integrated approach could support the development of smaller, more reusable sensors for portable and continuous air-quality monitoring, pending further validation in real-world environments.

Study Reference: Published in Microsystems & Nanoengineering, 24 March 2026 (DOI: 10.1038/s41378-025-01137-5).