Dynamic characteristics of droplet impacting on prepared hydrophobic/superhydrophobic silicon surfaces

- Hydrophobic/superhydrophobic surfaces are prepared on silicon specimens.
- Influence of micro pillars' height and spacing on the contact angle and the roll angle are studied in detail.
- Droplet impact dynamics on horizontal and incline superhydrophobic surfaces are investigated experimentally.
- Dripping processes are also simulated by the Computational Fluid Dynamics software Fluent 6.3.
- Effects of the contact angle and the roll angle on the dynamic characteristics of droplet are researched.

Micro pillar arrays were fabricated on silicon surfaces based on the reactive ion etching technology. Low surface energy coatings were deposited on textured surfaces in order to prepare hydrophobic/superhydrophobic surfaces. After measuring the static contact angles and roll angles, the dynamic characteristics of droplets impacting on these hydrophobic/superhydrophobic surfaces were investigated in detail. Both the static contact angle and the roll angle increased with the increase of micro pillars' height. With the increase of micro pillars' spacing, the roll angle decreased, but the change of static contact angle was irregular. On superhydrophobic surfaces, the spreading coefficient of droplet was affected by both the static contact angle and the roll angle, and the rebounding coefficient of droplet was highly relevant with the roll angle. In addition, the bigger the incline angle of surface, the smaller the spreading coefficient and the smaller the rebounding coefficient of droplet.