Observation of reflected and transmitted waves caused by acoustic streaming in droplet on surface acoustic waves devices

摘要

Droplet manipulation is one of the important applications using surface acoustic waves (SAWs). It is necessary to determine the droplet position on a SAW device. When a short burst signal was applied, a reflected signal was observed. The mechanism of the reflected wave observed was investigated from the visualization of the acoustic streaming. The propagation path in the droplet was assumed from the observation results and compared with the experimental results. The results agree with the calculated results, when the water droplet volume is above 2.5 mu l. Also, a transmitted signal is observed. The transmission depends on the longitudinal wave velocity of a liquid. The droplet position is determined from the measured results of the reflected and transmitted signals. Also, the results suggest that the longitudinal wave velocity is estimated from the reflection and transmission times, when the droplet position is known. (C) 2018 The Japan Society of Applied Physics.