Effect of Ultrasonic Wave Irradiation Sequence in Microhollow Production Produced by Bubble Cavitation

Sonoporation, which makes micropores through a cell membrane by bubble cavitation, improves the efficacy in ultrasonic wave drug delivery systems. However, the effects of bubble cavitation are affected largely by bubble condition, such as bubble density and bubble aggregation, just before the irradiation of a high-intensity ultrasonic wave. Aiming at preparing a specific bubble condition in bubble cavitation, a method which uses the frequency modulation of a pumping ultrasonic wave was proposed. In this paper, the effects of the ultrasonic wave irradiation sequence are evaluated under different flow velocities and bubble densities. The spatial correlation between microbubble clouds produced by the pumping ultrasonic wave and the microhollows produced by the bubble cloud cavitation is also discussed. (C) 2011 The Japan Society of Applied Physics