Splash of impacting nanodroplets on solid surfaces

Using molecular dynamics simulations we study the splash of water nanodroplets (ND) on hydrophilic to hydrophobic surfaces. Mechanisms for internal breakup and prompt splash are found to be different from those of macroscale (MS) impacting droplets. Breakup is attributed to initial air holes on solid surfaces for MS, but to vibration of a nanometer spreading film for ND. The prompt splash is initiated by air bubbles under spreading lamella at MS, but for ND by Rayleigh-Taylor instability of ejected rims from rapidly decelerated spreading lamella. ND internal breakup depends on surface wettability because vibration attenuation is larger on hydrophilic than hydrophobic surfaces.