Competition Between Acoustic Radiation Forces and Hydrodynamic Drag in Short-Pulsed-Ultrasound-Driven Microbubble Cluster Dynamics in Microfluidic Channel
Abstract
Microbubble dynamics under short-pulse ultrasound in flowing environments are governed by the interplay between acoustic radiation forces and hydrodynamic drag, yet their coupled effects remain insufficiently understood. Here, we investigate microbubble cloud behaviour in a vessel-mimicking microfluidic channel under short-pulse ultrasound (1.125 MHz) and controlled laminar flow (37.5–150 µL/min). High-speed visualization reveals two distinct regimes: an actively interacting regime characterized by clustering and coalescence, and a ‘frozen’ regime in which microbubbles exhibit minimal displacement despite continued ultrasound excitation. A theoretical model incorporating lift force, Bjerknes forces, wall-induced hydrodynamic interaction, and hydrodynamic drag with wall correction captures the transition between actively moving and frozen states, confirming that both a low flow rate and short-pulse ultrasound sequences promote the development of ‘frozen’ bubble nearby the wall, and demonstrating that microbubble cloud dynamics under short-pulse excitation is determined by a dynamic competition between acoustic radiation forces and near-wall hydrodynamic drag, with flow rate and pulse duration acting as coupled control parameters.
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The authors declare no competing interests to disclose.
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