Effects of Particle Shape on Growth Dynamics at Edges of Evaporating Colloidal Drops

TL;DR

This study investigates how particle shape influences the growth dynamics at the edges of evaporating colloidal drops, revealing distinct universality classes for different particle geometries.

Contribution

It demonstrates that particle shape determines the universality class of the growth process at the deposit edge, including Poisson, KPZ, and quenched disorder regimes.

Findings

Sphere particles show Poisson-like growth.

Slightly anisotropic particles follow KPZ universality.

Highly anisotropic ellipsoids exhibit KPZ with quenched disorder.

Abstract

We study the influence of particle shape on growth processes at the edges of evaporating drops. Aqueous suspensions of colloidal particles evaporate on glass slides, and convective flows during evaporation carry particles from drop center to drop edge, where they accumulate. The resulting particle deposits grow inhomogeneously from the edge in two-dimensions, and the deposition front, or growth line, varies spatio-temporally. Measurements of the fluctuations of the deposition front during evaporation enable us to identify distinct growth processes that depend strongly on particle shape. Sphere deposition exhibits a classic Poisson like growth process; deposition of slightly anisotropic particles, however, belongs to the Kardar-Parisi-Zhang (KPZ) universality class, and deposition of highly anisotropic ellipsoids appears to belong to a third universality class, characterized by KPZ fluctuations in the presence of quenched disorder.