Publication Date
11-12-2025
Document Type
Article
Publication Title
The Journal of Chemical Physics
Volume
163
Issue
18
DOI
10.1063/5.0298519
Abstract
A multispecies diffuse interface model is formulated in a fluctuating hydrodynamics framework for the purpose of simulating surfactant interfaces at the nanoscale. The model generalizes previous work to ternary mixtures, employing a Cahn–Hilliard free energy density combined with incompressible, isothermal fluctuating hydrodynamics where dissipative fluxes include both deterministic and stochastic terms. The intermolecular parameters in the free energy are chosen such that one species acts as a partially miscible surfactant. From Laplace pressure measurements, we show that in this model the surface tension decreases linearly with surfactant concentration, leading to Marangoni convection for interfaces with concentration gradients. In the capillary wave spectrum for interfaces with and without surfactant, we find that for the former, the spectrum deviates significantly from classical capillary wave theory, presumably due to Gibbs elasticity. In non-equilibrium simulations of the Rayleigh–Plateau instability, deterministic simulations showed that the surfactant delays pinching of a fluid cylinder into droplets. However, stochastic simulations indicate that thermal fluctuations disrupt the surfactant’s stabilizing effect. Similarly, the spreading of a patch of surfactant, driven by Marangoni convection, was found to be partially suppressed by thermal fluctuations.
Keywords
Thermal fluctuations, Surfactants, Interfacial tension, Hydrodynamics, Capillary waves, Stochastic processes
Department
Physics and Astronomy
Recommended Citation
John Bell, Andrew Nonaka, and Alejandro Garcia. "A Fluctuating Hydrodynamics Model for Nanoscale Surfactant-laden Interfaces" The Journal of Chemical Physics (2025). https://doi.org/10.1063/5.0298519
Accepted manuscript
Comments
This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in The Journal of Chemical Physics, Volume 163, Issue 18, Article 184104 , 2025 and may be found at https://doi.org/10.1063/5.0298519.