Novel methods of micro-object trapping by acoustic radiation force

Abstract

It is expected that micro object trapping by acoustic radiation force is a useful method in future drug delivery systems in order to concentrate the payloads at desired position. In this paper, two novel methods of micro object trapping are presented. First method is micro object trapping by seed bubbles. This method uses seed bubbles, which have higher sensitivity to the ultrasonic wave, in order to trap micro objects, which are difficult to trap by conventional methods due to low volumetric oscillation under the ultrasonic wave. The Bjerkne’s force, which is produced by a secondary wave radiated from the seed bubbles, traps the target objects making bi-layer seed bubbletarget object mass. The Second method is micro bubble trapping by bubble nonlinear oscillation. Two ultrasonic waves with different frequencies (pumping and control waves) are introduced simultaneously. The frequency of the control wave is set to a harmonic frequency of the pumping wave. If the bubbles flow into the cross area of two waves, nonlinear oscillation by high intensity pumping wave generates the Bjerkne’s force, producing multiple traps with narrow separation along the control wave propagation direction. In order to demonstrate these methods, experiments using an ultrasonic wave contrast agent are shown.