Dual high-frequency Surface Acoustic Wave Resonator for ultrafine particle sensing

This paper describes the development of a low-cost robust Surface Acoustic Wave Resonator (SAWR) micro sensor capable of detecting sub-micron size particles below 1 ng. The device comprises two 262 MHz Rayleigh wave SAW resonators fabricated on ST-cut quartz where one is used for particle sensing and the other as a reference channel. Electro-acoustic detection of different particles (including carbon, gold, sucrose, silicon, and PTFE) with different diameters was studied. The mass sensitivity of the SAWR was found to be typically 275 Hz/ng or 4 pg/Hz for the detection of 750 nm diameter gold particles. We believe that the device could be used as a low-cost and low power microsensor for the real-time and ubiquitous monitoring of airborne particulate matter. In particular, our SAWR sensor can be used to detect the typical levels of ultrafine particulate pollutants (PM2.5) found in city air today.