Simulations of Solid-on-Solid Models of Spreading of Viscous Droplets

TL;DR

This paper uses Monte Carlo simulations of SOS models to study viscous droplet spreading, reproducing key features like precursor layers and layering, and introduces a modified model that better captures droplet morphology and dynamics.

Contribution

The paper introduces a modified SOS model that incorporates surface potential effects into the dynamics, enabling more realistic simulation of viscous droplet spreading.

Findings

Precursor width increases proportional to square root of time.

Standard SOS model reproduces precursor layers and spherical cap profiles.

Modified model captures droplet morphology and dynamical layering effects.

Abstract

We have studied the dynamics of spreading of viscous non-volatile fluids on surfaces by MC simulations of SOS models. We have concentrated on the complete wetting regime, with surface diffusion barriers neglected for simplicity. First, we have performed simulations for the standard SOS model. Formation of a single precursor layer, and a density profile with a spherical cap shaped center surrounded by Gaussian tails can be reproduced with this model. Dynamical layering (DL), however, only occurs with a very strongly attractive van der Waals type of substrate potential. To more realistically describe the spreading of viscous liquid droplets, we introduce a modified SOS model. In the new model, tendency for DL and the effect of the surface potential are in part embedded into the dynamics of the model. This allows a relatively simple description of the spreading under different conditions, with a temperature like parameter which strongly influences the droplet morphologies. Both rounded droplet shapes and DL can easily be reproduced with the model. Furthermore, the precursor width increases proportional to the square root of time, in accordance with experimental observations. PACS: 68.10.Gw, 05.70.Ln, 61.20.Ja.