Dynamic behaviours of water droplets impacting on laser ablated surfaces

In order to reveal the underlying mechanism of surface microstructure-determined wetting states, this paper adopted Volume of Fluid (VOF) method to investigate the dynamic behaviours of water droplets impacting on surfaces with different structures at low and high Weber numbers. The simulation results showed that the high and stable pressure of air pockets is critical for the formation of the superhydrophobicity. A superhydrophobic substrate will result in shorter recoiling time and longer rebound time for water droplet than the hydrophobic substrate. Furthermore, superhydrophobic surface resulted in higher kinetic energy for water droplet than hydrophobic surfaces, which is the underlying mechanism of microstructure-enabled self-cleaning function. High-speed camera tests of laser processed surface microstructures were conducted to validate the observation in dynamic impacting simulation. The results in both high-speed camera testing and VOF simulation proved that water droplet will have a lower adhesion force when impacting superhydrophobic surface than hydrophobic surface.