Elastic properties of 2D colloidal crystals from video microscopy

TL;DR

This study measures the elastic constants of 2D colloidal crystals by analyzing particle fluctuations via video microscopy, revealing good agreement with theoretical zero-temperature models.

Contribution

It introduces a method to determine elastic constants of 2D colloidal crystals from microscopic strain fluctuations using video microscopy and finite-size scaling.

Findings

Elastic constants are accurately measured from particle fluctuations.

Results align well with zero-temperature theoretical calculations.

Finite-size effects are effectively accounted for in the analysis.

Abstract

Elastic constants of two-dimensional (2D) colloidal crystals are determined by measuring strain fluctuations induced by Brownian motion of particles. Paramagnetic colloids confined to an air-water interface of a pending drop are crystallized under the action of a magnetic field, which is applied perpendicular to the 2D layer. Using video-microscopy and digital image-processing we measure fluctuations of the microscopic strain obtained from random displacements of the colloidal particles from their mean (reference) positions. From these we calculate system-size dependent elastic constants, which are extrapolated using finite-size scaling to obtain their values in the thermodynamic limit. The data are found to agree rather well with zero-temperature calculations.