High frequency surface acoustic wave resonator-based sensor for particulate matter detection

Abstract

2016) High frequency surface acoustic wave resonator-based sensor for particulate matter detection.  New SAWR based particle sensor, capable of detection of sub-micron size particles with masses below 1 ng.  Sensitive, low-cost and robust acoustic sensor for particulate matter (PM10, PM2.5, UFP) detection for air-quality monitoring.  Novel SAWR design with free and shorted sensing areas, used in differential mode of operation.  Potential for low-power monolithic CMOS implementation.  Frequency dependent sensitivity of SAW resonators can be tailored to the size of particles to make them capable for UFPs, PM2.5 and PM10 detection.Abstract: This paper describes the characterization of high frequency Surface Acoustic Wave Resonator-based (SAWR) sensors, for the detection of micron and sub-micron sized particles. The sensor comprises two 262 MHz ST-cut quartz based Rayleigh wave SAWRs where one is used for particle detection and the other as a reference. Electro-acoustic detection of different sized particles shows a strong relationship between mass sensitivity (Δf/Δm) and particle diameter (Dp). This enables frequency-dependent SAWR sensitivity to be tailored to the size of particles, thus making these types of sensors good candidates for PM10, PM2.5 and ultrafine particle (UFP) detection. Our initial characterisation demonstrated a typical SAWR frequency shift of 60 Hz in response to a deposition of ca. 0.21ng of 0.75 µm-sized gold particles (~50 particles) on sensor's surface. Sensor responses to different size particles, such as ~30 µm diameter silicon, gold (diameters of ~0.75 µm and ~20 µm), ~8 µm fine sugar, PTFE (~1 µm and ~15 µm), ~4 µm talcum powder, and ~2 µm molybdenum powder were evaluated, and an average mass sensitivity of 275 Hz/ng was obtained. Based on the results obtained in this study we believe that acoustic wave technology has great potential for application in airborne particle detection. Moreover, acoustic resonator devices can be integrated with CMOS interface circuitry to obtain sensitive, robust, low-power and low-cost particle detectors for variety of applications including outdoor environmental monitoring.

A Novel Particulate Matter 2.5 Sensor Based on Surface Acoustic Wave Technology

“…The SAW sensor chip is embedded in the lower shell and aligned with the hot source in the upper shell, forming a plate-to-plate TP in the channel (9). When the airborne particles are inhaled into the VI, the airflow is divided into two.…”

“…The large particles follow into the middle channel (10) owing to their large inertia. Accordingly, because of small inertia, the small particles, namely PM2.5, follow into the left channel (8) and right channel (9) equally. When the PM2.5 flows through the TP in the channel (9), particles are captured on the surface of the SAW sensor chip by thermophoretic force.…”

“…Accordingly, because of small inertia, the small particles, namely PM 2.5 , follow into the left channel (8) and right channel (9) equally. When the PM 2.5 flows through the TP in the channel (9), particles are captured on the surface of the SAW sensor chip by thermophoretic force. Meanwhile, the particles in the left and middle channels are expelled from the outlet together.…”

“…At present, the main methods for PM 2.5 monitoring are the gravimetric method, the β-ray decay method and the tapered element oscillating microbalance (TEOM) method [5], which suffer from large volume and high price. On the other hand, for portable purposes, the light scattering method, the micro electro mechanical systems (MEMS) method and some novel detecting approaches [6][7][8][9] are reported. Besides, to realize better sensitivity for mass sensors, high-frequency and high-Q aluminum nitride Lamb wave resonators were also developed recently [10,11].…”

Compositional Analysis of Adsorbed Organic Aerosol on a Microresonator Mass Sensor

“…While the current setup is relatively bulky due to its modular design, future iterations of the impactor can be reduced in size as shown by MaldonadoGarcia et al (2016), for example. Network analyzers can also be replaced by oscillator circuits for automated measurement of frequency changes (i.e., mass) that are integrated with the resonator (Wasisto et al 2016;Thomas et al 2016;Wasisto et al 2014). …”