Efficient Fabrication of Tilt Micro/Nanopillars on Polypropylene Surface with Robust Superhydrophobicity for Directional Water Droplet Rebound

Abstract

The directional rebound and transport of water droplets play an important role in microfluidic devices, anti-fogging and water harvesting. Herein, an extrusion compression and directional stretch demolding method was used to prepare a polypropylene (PP) surface with tilt micro/nanopillars with a contact angle of 157 ± 3°. The rolling angle is the highest (9 ± 4°) when the direction of rotation is opposite the tilt direction of the micro/nanopillars, showing excellent water repellency and anisotropy of the surface. Compared with the position of the first collision of the water droplet, the position of the second collision shifted ~1.5 mm along the tilt direction of the micro/nanopillars, driven by the surface tension component during the collision. The directional rebound behavior is controlled by the droplet energy and the tilt angle. The micro/nanopillars show excellent self-cleaning property and mechanical durability, which shows the possibility of their practical engineering applications.

Keywords: rapid fabrication, tilt micro/nanopillars, Anisotropy, directional water rebound