The buckling and invagination process during consolidation of colloidal droplets

TL;DR

This paper investigates the buckling and invagination phenomena during the drying of colloidal droplets, providing insights into the deformation process and validating theoretical models through direct observation and energy analysis.

Contribution

It offers a detailed experimental validation of buckling theory in 2D droplets and extends the understanding to 3D droplets where direct measurement is challenging.

Findings

Identified the critical shell thickness for buckling.

Observed a universal deformation pattern across various colloids.

Validated energy-based models for droplet shape evolution.

Abstract

Drying a droplet of colloidal dispersion can result in complex pattern formation due to both development and deformation of a skin at the drop surface. The present study focus on the drying process of droplets of colloidal dispersions in a confined geometry where direct observations of the skin thickness are allowed. During the drying, a buckling process is followed by a single depression growth inside the drop. The deformation of the droplet is found to be generic and is studied for various colloidal dispersions. The final shape can be partly explained by simple energy analysis based on the competition between bending and stretching deformations. Particularly, the final shape enables us to determine precisely the critical thickness of the shell for buckling. This study allow us to validate theory in 2D droplets and apply it to the case of 3D droplets where the thickness is not accessible by direct observation.