Acoustically mediated long-range interaction among multiple spherical particles exposed to a plane standing wave

TL;DR

This paper derives an analytical model for long-range acoustic interactions among multiple spherical particles in a standing wave, revealing pairwise interactions and potential for self-organization of particle clusters.

Contribution

It provides an accurate analytical expression for multi-particle acoustic forces beyond the Rayleigh limit, demonstrating vector additivity and long-range interaction characteristics.

Findings

Interaction forces are accurately modeled beyond the Rayleigh limit.

Multi-particle interactions decompose into independent pairwise systems.

Long-range, oscillatory decay of acoustic forces is characterized.

Abstract

In this work, we study the acoustically mediated interaction forces among multiple well-separated spherical particles trapped in the same node or antinode plane of a standing wave. An analytical expression of the acoustic interaction force is derived, which is accurate even for the particles beyond the Rayleigh limit. Interestingly, the multi-particle system can be decomposed into a series of independent two-particle systems described by pairwise interactions. Each pairwise interaction is a long-range interaction, as characterized by a soft oscillatory attenuation (at the power exponent of n=-1 or -2). The vector additivity of the acoustic interaction force, which is not well expected considering the nonlinear nature of the acoustic radiation force, is greatly useful for exploring a system consisting of a large number of particles. The capability of self-organizing a big particle cluster can be anticipated through such acoustically controllable long-range interaction.