超音波の作用によるマイクロバブルの破壊とキャビテーション気泡の生成

抄録

Microbubble destruction and the induced cavitation bubble behavior are regarded as key phenomena affecting the enhancement of sonoporation. In the present study an experiment was carried out for investigating the interaction of ultrasound waves with microbubbles. Test liquid was a suspension of Sonazoid ultrasound contrast agent diluted with distilled water with the volumetric concentration of 10 % [v/v], which was set in a cylindrical vessel, i.e. one of a 24 well-plate, conventionally used in in vitro experiments and irradiated by ultrasound waves with the frequency of 1 MHz. It was found that microbubbles were rapidly destroyed and the survival number was reduced to half the original number within 100ms for all the liquid depths examined here. A maximum number of cavitation bubbles was achieved at a certain exposure time less than one second where more than sixty cavitation bubbles were generated, subsequently behaving in the observation volume (= 14 mm³). Although almost the microbubbles were crushed within one second, we occasionally observed a special situation where plenty of cavitation bubbles happened at the exposure time of five seconds due to the circulation flow generated by the acoustic radiation pressure coupled with the flow induced by the free surface fluctuation.