The influence of distance between microbubbles on the fluid flow produced during ultrasound exposure

Abstract

The collapse dynamics of lipid monolayer-coated microbubbles in the clinically-relevant size range under 6 μm in diameter have not been studied directly due to their small size obscuring the collapse visualization. This study investigates the influence of inter-microbubble distance on the shape of lipid debris clouds created by the collapse of the microbubble destroying the microbubble lipid monolayer. The shape was highly influenced by the fluid motion that occurred as the microbubbles collapsed. It was observed that at inter-microbubble distances smaller than 37 μm the microbubbles began to interact with one another resulting in distorted and ellipsoid-shaped debris clouds. At inter-microbubble distances less than 10 μm, significantly elongated debris clouds were observed that extended out from the original microbubble location in a single direction. These distortions show a significant distance-dependent interaction between microbubbles. It was observed that microbubbles in physical contact with one another behaved in the same manner as separate microbubbles less than 10 μm apart creating significantly elongated debris clouds. It can be hypothesized that small inter-microbubble distances influence the microbubble to collapse asymmetrically resulting in the creation of fluid jets that contribute to the formation of debris fields that are elongated in a single direction.

Elastic Deformation of Soft Tissue-Mimicking Materials Using a Single Microbubble and Acoustic Radiation Force

“…Microbubbles were extracted from the vial with a 20G syringe needle and then diluted in 0.9% saline. Microbubbles were diluted such that they were well spaced within the channel, at least 100 µm between bubbles to reduce coupling ( Schutt et al 2014 ). This was achieved at a concentration of approximately 10 6 microbubbles/mL.…”

Stimuli‐Responsive Biomaterials: Scaffolds for Stem Cell Control

“…[184,185] Generated mechanical effects of relevance to delivery include acoustic cavitation, which is the forced size oscillation or growth and collapse of gas microbubbles within a fluid, [186] as well as related fluid streaming. [187][188][189][190] Ultrasound waves penetrate readily through biological tissue and tissue-like constructs and can be applied in a focused manner, [191,192] allowing for in situ manipulation of materials and cells deep within. By controlling the intensity and duration of the applied energy, ultrasound can be employed with high biocompatibility.…”

Removal of ligand-bound liposomes from cell surfaces by microbubbles exposed to ultrasound

“…The ultrasound pulses used here had a peak negative pressure of 0.8 MPa and inertial cavitation has been shown to occur with microbubbles at ultrasound peak negative pressures as low as 0.6 MPa [40]. Passive acoustic detection has confirmed that microbubble inertial cavitation occurs in this experimental setup under these conditions [41]. If inertial cavitation did occur with the 1-3 μm diameter microbubbles, the resulting shockwaves and intense fluid flow could explain the observed large distances over which liposomes were removed and the partial cell detachments.…”