Optical observation of collapses of two bubbles adhered to the quartz wall under ultrasound irradiation with high-speed video camera: Micro-jet arising from two collapsing bubbles

• Published in: The Journal of the Acoustical Society of America 2006-11, Vol.120 (5_Supplement), p.3165-3165
• Main Authors: Yoshida, Kenji, Nakatani, Shintaro, Watanabe, Yoshiaki
• Format: Article
• Language: English
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/1.4787896

The mechanical action of a micro-jet, which arises from the collapse of bubbles, has been widely used for ultrasonic cleaning and sonoporation in medical field. The generation mechanism of a micro-jet induced by the ultrasound irradiation is focused on. In previous theoretical and experimental researches, the generation mechanism is well known when a single bubble is adhered to a rigid wall. However, its mechanism is not understood in detail when multiple bubbles exist on rigid wall. The optical observation of multi-bubble collapse greatly contributes to the development of micro-jet applications. It was observed that the collapses of two bubbles adhered to the quartz wall in an ultrasound field with high speed video camera (HPV-1, SHIMADZU). Maximum recording rate of this high speed video camera is 1 000 000 frames/second. The emitted ultrasound frequency is 27 kHz. From the observation, one of two bubbles was deformed after these bubbles vibrate. The micro-jet was generated to the opposite side against the deformed bubble when the deformed one touches the other. Then, the direction of the micro-jet to the quartz wall was almost horizontal. The number of micro-jets increased every time the distorted bubble touched the other. Finally, five micro-jets to the various directions were observed at the same instant.