| Cavitation micro bubble enhances the permeability of cell membrane if the bubble is placed in the vicinity of the cell. Aiming at adhering micro bubbles to the target wall, a method by frequency sweep of ultrasonic pumping wave is proposed. Slow frequency decrease from fH to fL expands the aggregated bubbles to the surrounding target wall. Quick frequency return from fL to fH followed by the slow frequency decrease increases the amount of adhered bubbles to the target wall. Three dimensional numerical analyses are carried out by taking into account of the secondary Bjerknes forces between bubbles. Basic experiment is done using an ultrasonic contrast agent micro bubble. |