Nebulization using ZnO/Si surface acoustic wave devices with focused interdigitated transducers

Zhou, Jian, Tao, Xiang, Luo, Jingting, Li, Yifan, Jin, Hao, Dong, Shurong, Luo, JiKui, Duan, Huigao and Fu, Yong Qing (2019) Nebulization using ZnO/Si surface acoustic wave devices with focused interdigitated transducers. Surface and Coatings Technology, 367. pp. 127-134. ISSN 0257-8972

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Abstract

Propagation of surface acoustic waves (SAWs) on bulk piezoelectric substrates such as LiNbO3 and quartz, exhibits an in-plane anisotropic effect due to their crystal cut orientations. Thin film SAW devices, such as those based on ZnO or AlN, offer potential advantages, including isotropic wave velocities in all in-plane directions, higher power handling capability, and potentially lower failure rates. This paper reports experimental and simulation results of nebulization behaviour for water droplets using ZnO/Si surface acoustic wave devices with focused interdigital transducers (IDTs). Post-deposition annealing of the films at various temperatures was applied to improve the quality of the sputtering-deposited ZnO films, and 500 °C was found to be the optimal annealing temperature. Thin film ZnO/Si focused SAW devices were fabricated using the IDT designs with arc angles ranging from 30° to 90°. Nebulization was significantly enhanced with increasing the arc angles of the IDTs, e.g., increased nebulization rate, reduced critical powers required to initialise nebulization, and concentration of the nebulised plume into a narrower size of spray. Effects of applied RF power and droplet size have been systematically studied, and increased RF power and reduced droplet size significantly enhanced the nebulization phenomena.

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