Influences of oscillatory structural forces on dewetting of nanoparticle-laden ultra-thin films

Abstract

To understand the influences of nanoparticles on dewetting in ultra-thin films, both linear stability theory and numerical simulations are performed in the present study, with the consideration of oscillatory structural (OS) forces. Long scale approximation is utilized to simplify the hydrodynamic and diffusion equations to a nonlinear system for film thickness and nanoparticle concentration. Results show that the presence of nanoparticles generally suppresses the dewetting process. Two physical mechanisms responsible for this phenomenon are addressed in the present study. When the oscillatory structural forces are relatively smaller, the essential feature of film evolution is similar to the case of particle-free flow. The reduction of the linear growth rate and the postponement of film rupturing can be attributed to the increment of the viscosity due to the presence of nanoparticles. On the other hand, when the intensity of the OS forces becomes stronger, the stepwise thinning of film can be observed which prevents the film from rupture. Numerical simulations indicate that this phenomenon is caused by the existence of a stable zone due to the oscillatory nature of the structural forces. Another interesting finding is that the nonuniformity of the distribution of nanoparticle concentration might destabilize a spinodally stable film, and trigger the occurrence of film dewetting.