In this study, we investigate the interfacial droplet jetting characteristics and thermal stability of a focused surface acoustic wave device (F-SAW). An F-SAW device capable of generating a 20 MHz surface acoustic wave by applying sufficient radio frequency power (2–19 W) on a 128°-rotated YX-cut piezoelectric lithium niobate substrate for interfacial droplet jetting is proposed. The interfacial droplet jetting characteristics were visualized by a shadowgraph method using a high-speed camera, and a heat transfer experiment was conducted using K-type thermocouples. The interfacial droplet jetting characteristics (jet angle and height) were analyzed for two different cases by applying a single interdigital transducer and two opposite interdigital transducers. Surface temperature variations were analyzed with radio frequency input power increases to evaluate the thermal stability of the F-SAW device in air and water environments. We demonstrate that the maximum temperature increase of the F-SAW device in the water was 1/20 of that in the air, owing to the very high convective heat transfer coefficient of the water, resulting in prevention of the performance degradation of the focused acoustic wave device.
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Acknowledgments: This work was supported by the Center for Advanced MetaMaterials (CAMM) funded by the Ministry of Science, ICT and Future Planning as Global Frontier Project (CAMM-No. NRF2014M3A6B3063716), and the Human Resources Development program (No. 20174030201720) of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), grant funded by the Korea government Ministry of Trade, Industry and Energy.
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