Diving with microparticles in acoustic fields

TL;DR

This paper demonstrates a 3D visualization technique for microparticles manipulated by acoustic fields, enabling detailed observation and quantitative analysis of acoustophoresis phenomena.

Contribution

It introduces a simple astigmatism-based method for 3D visualization and measurement of particles in acoustic fields, enhancing understanding of acoustophoresis.

Findings

Effective 3D visualization of microparticle motion

Quantitative measurements align with theoretical predictions

Technique reveals detailed particle trajectories in acoustic fields

Abstract

Sound can move particles. A good example of this phenomenon is the Chladni plate, in which an acoustic wave is induced in a metallic plate and particles migrate to the nodes of the acoustic wave. For several years, acoustophoresis has been used to manipulate microparticles in microscopic scales. In this fluid dynamics video, submitted to the 30th Annual Gallery of Fluid Motion, we show the basic mechanism of the technique and a simple way of visualize it. Since acoustophoretic phenomena is essentially a three-dimensional effect, we employ a simple technique to visualize the particles in 3D. The technique is called Astigmatism Particle Tracking Velocimetry and it consists in the use of cylindrical lenses to induce a deformation in the particle shape, which will be then correlated with its distance from the observer. With this method we are able to dive with the particles and observe in detail particle motion that would otherwise be missed. The technique not only permits visualization but also precise quantitative measurements that can be compared with theory and simulations.