Front instabilities in evaporatively dewetting nanofluids

TL;DR

This paper investigates the formation of branched structures in evaporating nanofluids, using a modified Monte Carlo model to analyze the instability of dewetting fronts driven by solvent evaporation and nanoparticle diffusion.

Contribution

It introduces a modified Monte Carlo model to study the transverse fingering instability in evaporating nanofluid films, highlighting the effects of various parameters on pattern formation.

Findings

Dewetting fronts develop transverse fingering instabilities.

Pattern characteristics depend on chemical potential, nanoparticle mobility, and concentration.

The instability mechanism is explained through model analysis.

Abstract

Various experimental settings that involve drying solutions or suspensions of nanoparticles -- often called nanofluids -- have recently been used to produce structured nanoparticle layers. In addition to the formation of polygonal networks and spinodal-like patterns, the occurrence of branched structures has been reported. After reviewing the experimental results we use a modified version of the Monte Carlo model first introduced by Rabani et al. [Nature 426, 271 (2003)] to study structure formation in evaporating films of nanoparticle solutions for the case that all structuring is driven by the interplay of evaporating solvent and diffusing nanoparticles. After introducing the model and its general behavior we focus on receding dewetting fronts which are initially straight but develop a transverse fingering instability. We analyze the dependence of the characteristics of the resulting branching patterns on the driving chemical potential, the mobility and concentration of the nanoparticles, and the interaction strength between liquid and nanoparticles. This allows us to understand the underlying instability mechanism.