Colloidal Directional Structures at a Nematic Liquid Crystal-Air Interface

TL;DR

This paper investigates the formation of colloidal structures at a nematic liquid crystal-air interface, highlighting the role of dipole-quadrupole interactions in creating directional chains and fractal clusters.

Contribution

It reveals how dipole-quadrupole interactions, influenced by droplet polydispersity, lead to novel directional and fractal colloidal structures at the interface.

Findings

Directional chains and branches are formed with specific orientations.

Dipole-quadrupole interactions are central to structure formation.

Clusters exhibit fractal statistical properties.

Abstract

We present a variety of structures formed by colloidal droplets at a nematic liquid crystal-air interface, where the elastic dipole-dipole, quadrupole-quadrupole, and dipole-quadrupole interactions are all essentially involved. The colloidal structures observed not only include chains with kinks or clusters, but also comprise directional structures, such as directional chains and branches, whose direction is associated with the tilting director in the liquid crystal layer. The dipole-quadrupole interaction, originating from the polydispersity of the droplets, plays a central role for the formation of these directional structures. Clusters consisting of directional branches and chains are also observed and found to be fractal statistically.