Impact dynamics of nanodroplets on pillared surfaces

Impacting nanodroplets on pillared surfaces are investigated with molecular dynamics simulations. The difference between the liquid spreading dynamics on flat and pillared surfaces is shown to arise from the intrusion effect of liquid into pillar gaps. The altered dynamics can be understood by modeling the maximum spreading factor \ensuremath{\beta}${}_{m\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}x}$. The scaling laws of \ensuremath{\beta}${}_{m\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}x}$ on flat surfaces can successfully predict \ensuremath{\beta}${}_{m\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}x}$ on pillared surfaces when the volume term of the bulk droplet is properly accounted for. For a six parameter group of the initial problem we propose a universal phase space which contains six outcome regimes for impacting nanodroplets.