Mechanical properties of model colloidal mono-crystals

TL;DR

This study examines the elastic and yielding behaviors of defect-free colloidal mono-crystals under compression, revealing how they respond elastically until fracture and how their properties can be modeled analytically.

Contribution

It provides a combined experimental and analytical analysis of the elastic and yielding properties of colloidal mono-crystals, including simple models for their behavior.

Findings

Crystals exhibit elastic response until a critical force causes fracture.

Force peaks correspond to successive row-reduction transitions.

Elastic properties are well described by a capillary spring model.

Abstract

We investigate the elastic and yielding properties of two dimensional defect-free mono-crystals made of highly monodisperse droplets. Crystals are compressed between two parallel boundaries of which one acts as a force sensor. As the available space between boundaries is reduced, the crystal goes through successive row-reduction transitions. For small compression forces, the crystal responds elastically until a critical force is reached and the assembly fractures in a single catastrophic global event. Correspondingly there is a peak in the force measurement associated with each row-reduction. The elastic properties of ideal mono-crystal samples are fully captured by a simple analytical model consisting of an assembly of individual capillary springs. The yielding properties of the crystal are captured with a minimal bond breaking model.