Self-Assembly of Colloidal Superstructures in Coherently Fluctuating Fields

TL;DR

This paper develops a theory for a non-equilibrium Van der Waals-like force in fluctuating electromagnetic fields, explaining complex self-assembled structures in colloids and predicting new experimental phenomena.

Contribution

It introduces a comprehensive theory for coherent fluctuation-induced forces and describes the formation of novel colloidal morphologies, including dipolar foams, in non-equilibrium conditions.

Findings

Derivation of the equation of state for coherent Van der Waals forces

Prediction of dipolar foam structures in colloids

Application to and explanation of recent experimental results

Abstract

From microscopic fluid clusters to macroscopic droplets, the structure of fluids is governed by the Van der Waals force, a force that acts between polarizable objects. In this Letter, we derive a general theory that describes the non-equilibrium counterpart to the Van der Waals force, which emerges in spatially coherently fluctuating electromagnetic fields. We describe the formation of a novel and complex hierarchy of self-organized morphologies in magnetic and dielectric colloid systems. Most striking among these morphologies are dipolar foams - colloidal superstructures that swell against gravity and display a high sensitivity to the applied field. We discuss the dominance of many body forces and derive the equation of state for a material formed by the coherent Van der Waals force. Our theory is applied to recent experiments in paramagnetic colloidal systems and a new experiment is suggested to test the theory.