Dynamics of Acoustically Bound Particles

TL;DR

This paper introduces a new numerical method to analyze acoustic binding forces between particles, revealing their potential for creating stable clusters and inducing motion, with applications in material synthesis and drug delivery.

Contribution

It develops a novel computational approach to study multi-particle acoustic forces, demonstrating stable cluster formation and motion behaviors not previously explored.

Findings

Stable particle clusters with wavelength separation formed.

Particles exhibit driven linear, rotational, or vibrational motion.

Acoustic binding forces are non-conservative and non-pairwise.

Abstract

It is well known that acoustic fields can produce forces on single particles, however they can also induce inter-particle forces due to multiple scattering events. This multi-particle force -- here referred to as acoustic binding -- is comparable to other acoustic forces when the particles are of order wavelength in diameter. In principle, this force could be used as a tunable method for directing the assembly of particles of mm-scales, but has not been extensively explored in previous work. Here, we use a novel numerical method to compute binding interactions between strongly scattering bodies and find that they can produce stable clusters of particles with approximately wavelength separation. Moreover, we also observe that -- depending on the level of damping -- these structures can produce driven linear, rotational, or vibrational motion. These effects are a result of the non-conservative and non-pairwise nature of the acoustic binding force, and represent novel contactless manipulation and transport methods with potential application to metamaterial synthesis and drug delivery.