Surface wetting of liquid nanodroplets: Droplet-size effects

The spreading of liquid nanodroplets of different initial radii R-0 is studied using molecular dynamics simulation. Results for two distinct systems, Pb on Cu(111), which is nonwetting, and a coarse-grained polymer model, which wets the surface, are presented for Pb droplets ranging in size from similar to 55 000 to 220 000 atoms and polymer droplets ranging in size from similar to 200 000 to 780 000 monomers. In both cases, a precursor foot precedes the spreading of the main droplet. This precursor foot spreads as r(f)(2)(t)=2D(eff)t with an effective diffusion constant that exhibits a droplet-size dependence D(eff)similar to R-0(1/2). The radius of the main droplet r(b)(t)similar to R-0(4/5) is in agreement with kinetic models for the cylindrical geometry studied.