Droplets displacement and oscillations induced by ultrasonic surface acoustic waves: a quantitative study

TL;DR

This study investigates how ultrasonic surface acoustic waves influence droplet behavior, revealing complex internal flows, surface oscillations, and displacement mechanisms through combined experimental and numerical analysis.

Contribution

It provides new insights into the physics of droplet deformation and movement caused by ultrasonic waves, combining experimental observations with numerical modeling.

Findings

Droplets exhibit internal flow and surface oscillations under ultrasonic SAWs.

Drop displacement depends on wave amplitude and involves acoustic streaming and radiation pressure.

Surface deformation results from a combination of acoustic streaming and radiation pressure effects.

Abstract

We present an experimental study of a droplet interacting with an ultrasonic surface acoustic wave (SAW). Depending on the amplitude of the wave, the drop can either experience an internal flow with its contact-line pinned, or (at higher amplitude) move along the direction of the wave also with internal flow. Both situations appear together with oscillations of the drop free-surface. The physical origins of the internal mixing flow as well as the drop displacement and surface waves are still not well understood. In order to give insights of the underlying physics involved in these phenomena, we carried out an experimental and numerical study. The results suggest that the surface deformation of the drop can be related as a combination between acoustic streaming effect and radiation pressure inside the drop.