Formation of Colloidal Chains and Driven Clusters with Optical Binding

TL;DR

This study investigates how optical forces influence the self-organization of colloidal particles in three dimensions, revealing tunable structures and driven clusters formed through N-body interactions, advancing the understanding of optical binding in larger systems.

Contribution

It introduces a novel experimental approach to study large-scale colloidal self-organization and demonstrates the role of N-body interactions in driven cluster formation.

Findings

Colloidal particles form large optically bound structures.

Driven clusters emerge from N-body interactions.

Structure and behavior are tunable via particle refractive index and light properties.

Abstract

We study the effects of the optical binding force on wavelength sized colloidal particles free to move in a counter-propagating beam. This work is motivated by the concept of using optical binding to direct the assembly of large numbers of colloidal particles; previous work has used small numbers of particles and/or 1D or 2D restricted geometries. Utilizing a novel experimental scheme, we describe the general static and dynamic self-organization behaviors for 20--100 particles free to move in 3-dimensional space. We observe the self-organization of the colloids into large optically bound structures along with the formation of driven particle clusters. Furthermore we show that the structure and behavior of these optically bound systems can be tuned using the refractive index of the particles and properties of the binding light. In particular, we show that the driven behavior originates from $N$-body interactions, which has significant implications for future work on optically bound clusters of more than 2 particles.