Particle Effect and Force Computation on Nanosuspension Droplet Spreading: MD Simulations

The behavior of nano-fluids, or fluid suspensions containing nanoparticles, has garnered tremendous attention recently in advanced optoelectronic applications. One concern is how to control the ordering of nano-particle arrays and to fabricate those functional semiconductor devices. Nano-suspension provides us a path to synthesize and disperse nanoparticles in fluids, however, the fundamental mechanisms about interfaces and wetting kinetics is still unknown when a nanosuspension drop spreads on a solid surface. Herein, we present results from molecular dynamics simulations with emphasis on revealing forces on suspended particles. Pinning of the advancing three phase contact line occurs for low contact angle while de-pinning occurs at higher angles; forces associated with such behaviors are presented. For increasing particle size, a transition from de-pinning to pinning is observed and interpreted in terms of the increasing capillary force between suspended nanoparticles and the solid/liquid/vapor interfaces. At higher nanoparticle concentrations, particle/particle interactions become relevant and particle pile up occurs, leading to pinning and non-equilibrium droplet morphology.