Capillary nanowaves on surfactant-laden liquid films with surface viscosity and elasticity

Nanofilms are susceptible to surfactant contamination. This work investigates surfactant effects on nanowave dynamics on a bounded film with a finite depth, using both molecular dynamics simulations and analytical theories. It is shown that the presence of surfactants leads to a slower decay of surface mode temporal correlations, which, however, cannot be predicted by only considering the decreased surface tension due to the added surfactants. Based on the Boussinesq--Scriven model for surface viscosity, a linear stability analysis of Stokes flow for films with arbitrary depth is conducted. The obtained dispersion relation considering surface viscosity can justify the simulation results.