Sensitive Membrane Resonator Sensor for Sub-Micron Diameter Particle Counting

This paper describes a sensitive method for particle sensing using a high-order membrane resonator operating at 9.5 MHz. The design makes use of AIN piezoelectric film with a supported disk geometry to provide isolation of the electrical contacts. The frequency shifts measured with known particle deposition are based on a thermophoretic separator. The particle mass flux calculation using the thermophoretic separator are $4.98 \times 10^{-8}$ and $8.24 \times 10^{-8} \mathrm{mg} / \mathrm{mm}^{2}$ which was achieved at 50 °C and 70 °C respectively. The sensitivity observed for 50-200 nm diameter particles was 0.9 Hz frequency shift correlating to a 69 fg mass change at 50 °C, and a 1.2 Hz frequency shift correlating to a 92 fg mass change at 70 °C, compared to a theoretical mass sensitivity of 13Hz/pg.