Monte Carlo simulation of colloidal particles dynamics in a drying drop

TL;DR

This paper uses Monte Carlo simulations to study colloidal particle dynamics in drying drops, testing hypotheses about ring formation and microstructure, but finds that additional effects like surface tension may be needed for accurate modeling.

Contribution

It introduces a Monte Carlo simulation model for colloidal particles in drying drops and evaluates hypotheses about microstructure formation during drying.

Findings

Simulation did not reproduce quasicrystalline structures.

Diffusional and flow timescales alone do not explain microstructure.

Additional effects like surface tension are likely important.

Abstract

The work is devoted to particles dynamics simulation in a colloidal drop, when it dries on a substrate and the triple-phase boundary is fixed. Experimental observations [Deegan R. D. et. al., 2000] show a ring deposition on a solid substrate after full droplet desiccation. This phenomenon of macrolevel is known as coffee ring effect. There are other experiments that show a co-effect at the microlevel. We are talking about the formation of a quasicrystalline structure on the outer part of the ring and occurrence amorphous inner zone of ring [Mar\'{\i}n \'A. G. et. al., 2011]. The goal of this work is to check the hypothesis of other authors that this phenomenon is explained by the competition between the characteristic times of diffusional displacement of particles and their transfer by a compensation flow [Mar\'{\i}n \'A. G. et. al., 2011]. Numerical calculations using a model built on the basis of such assumptions and effects did not show the formation of a quasicrystal structure. It is probably necessary to take into account additional effects in such a system, for example, surface tension.