Self-cleaning superhydrophobic films by supersonic-spraying polytetrafluoroethylene-titania nanoparticles

Spherical water drops show little or no adhesion to superhydrophobic surfaces due to the strong water repellence. Polytetrafluoroethylene (PTFE)-titania (TiO₂) nanocomposite films were fabricated using a scalable, rapid and cost-effective technique: supersonic spray coating at room temperature. The wettability of the supersonic spray-coated nanocomposite films can be tuned to the Cassie-Baxter or Wenzel wetting states by simply varying the relative content of titania. This wettability tuning can also be used to adjust the surface morphology of the films, resulting in either a rough compact structure or a porous morphology. The static water contact angle and roll-off angles were measured for the nanocomposite films as a function of the titania content. Furthermore, water drop rebounding and water jet impact tests were performed on the nanocomposite films and their self-cleaning properties were investigated.