Directed Self-Assembly of Polarizable Ellipsoids in an External Electric Field

TL;DR

This study uses Monte Carlo simulations to explore how polarizable ellipsoids self-assemble into various structures under electric fields, revealing transitions from 3D crystals to 2D sheets and tubes based on shape and interaction anisotropy.

Contribution

It introduces a simple two-point-charge model that effectively captures complex self-assembled structures of ellipsoids in electric fields, advancing understanding of anisotropic colloidal assembly.

Findings

High electric fields induce shape-dependent structural transitions.

The model reproduces experimental structures at low volume fractions.

Anisotropic interactions lead to diverse self-assembled morphologies.

Abstract

The interplay between shape anisotropy and directed long-range interactions enables the self-assembly of complex colloidal structures. As a recent highlight, ellipsoidal particles polarized in an external electric field were observed to associate into well-defined tubular structures. In this study, we investigate systematically such directed self-assembly using Monte Carlo simulations of a two-point-charge model of polarizable prolate ellipsoids. In spite of its simplicity and computational efficiency, we demonstrate that the model is capable of capturing the complex structures observed in experiments on ellipsoidal colloids at low volume fractions. We show that, at sufficiently high electric field strength, the anisotropy in shape and electrostatic interactions causes a transition from 3-dimensional crystal structures observed at low aspect ratios to 2-dimensional sheets and tubes at higher aspect ratios. Our work thus illustrates the rich self-assembly behavior accessible when exploiting the interplay between competing long- and short-range anisotropic interactions in colloidal systems.