Controlling picolitre droplet impact dynamics by tailoring the solid subsurface

The oscillatory dynamics of picolitre water droplets following impact onto a range of hydrophobic surfaces is found to be influenced by the underlayer stiffness and thickness. The relative contributions of surface functionality versus subsurface hardness have been decoupled by utilising plasmachemical surface functionalisation and underlayer crosslinking respectively. Higher oscillation frequencies are measured for softer and thicker films, which correlates to a larger surface deformation around the liquid droplet contact line