Capillary Forces Computation for Nano-suspension Droplet Spreading: Molecular Dynamics Simulations

With the development of nano-technology, nano-suspension provides us a path to synthesize and disperse nano-particles in fluids, and it has been widely utilized in pharmaceutical and semiconductor industries. Recently, many studies via both experiments and simulations have focused on nano-suspension droplets dynamic spreading and further evaporation on solid surfaces. However, the underlying physics and especially the fundamental driving forces controlling the kinetics of nano-suspension wetting and spreading is still unknown. In this talk, results from molecular dynamics simulations are presented with emphasis on computing capillary forces between advancing liquid fronts and suspended particles. Meanwhile, the effect of nano-particle size, particle loading, and interaction strength examined from atomic scale simulations will be presented. For increasing particle size, a dramatic change of wetting behavior from de-pinning to pinning is observed and also interpreted as the increasing capillary force between suspended nano-particles and the three-phase interface. By tuning down the interaction between the particle and the underlying substrate, de-pinning is observed instead of the exhibiting pinning behavior.