Microbubble Self-Trapping to Surface of Target

Abstract

Microbubble self-trapping to the target surface is proposed. The Bjerknes force, which is produced by bubble nonlinear oscillation upon pumping ultrasonic wave radiation, acts as a trapping force on the target surface. A condition for the minimum separation between the neighboring bubbles is required in order to initiate self-trapping. Experiments are carried out using an ultrasonic wave contrast agent. Silicone resin, acrylic resin, and agar gel are examined as targets. Mechanisms by which already self-trapped bubbles promote further self-trapping are observed.

Micro bubble adhesion to target wall by frequency sweep of ultrasonic pumping wave

“…In the experimental result [4], we observe that the micro bubbles align with almost the same interval which is much shorter than the wavelength of the ultrasonic pumping wave. This result implies that the secondary Bjerknes force between bubbles is produced by n-th order harmonic component of the bubble nonlinear oscillation.…”

“…In the previous experiment which is carried out using an ultrasonic contrast agent, we observe that the bubbles align on the target surface with interval much shorter than the wavelength of the ultrasonic wave when the ultrasonic pumping wave is introduced [4]. This short internal between bubbles implies that the secondary Bjerknes force between bubbles is produced by the harmonic oscillation of bubbles.…”

“…Since this force pushes the micro bubble in the direction of the ultrasonic wave propagation, micro bubbles attach to one side of the blood vessel if the blood vessel is perpendicular to the ultrasonic wave propagation direction. We have proposed a method of self-adhesion of micro bubbles to the target wall [4]. This method uses the secondary Bjerknes force to adhere the bubbles to the target wall.…”

Observation of flow variation in capillaries of artificial blood vessel by producing microbubble aggregations

“…By making use of microbubble aggregations, the effects of ultrasound therapy would be expected by accelerating the temperature increase in thermal therapy [1,2] and inducing sonoporation [3] to allow the uptake of larger molecules into cells in physical drug delivery [4,5]. Though the mechanism to form aggregation is very complex, because of the connection among various parameters, various researches related to microbubble aggregations were experimentally and theoretically investigated [6][7][8][9][10][11]. However, because of the difficulty to produce a capillary-mimicking artificial blood vessel, the behavior of aggregations in a capillary, e.g., probability to obstruct in bloodstream, shape destruction of the aggregation, etc, has not been predicted.…”

Study to prevent the density of microcapsules from diffusing in blood vessel by local acoustic radiation force

“…Considering micrometer-sized microcapsules, upon ultrasound exposure, they are oscillated to produce Bjerknes force and to aggregate each other [10] if the frequency of ultrasound is near their resonance frequency. We already confirmed aggregation of capsules in a straight flow when acoustic radiation force was produced in oncoming direction with MHz-order frequencies [8].…”