title: Three-tier rough superhydrophobic surfaces.
abstract: A three-tier rough superhydrophobic surface was fabricated by growing hydrophobic modified (fluorinated silane) zinc oxide (ZnO)/copper oxide (CuO) hetero-hierarchical structures on silicon (Si) micro-pillar arrays. Compared with the other three control samples with a less rough tier, the three-tier surface exhibits the best water repellency with the largest contact angle 161° and the lowest sliding angle 0.5°. It also shows a robust Cassie state which enables the water to flow with a speed over 2 m s(-1). In addition, it could prevent itself from being wetted by the droplet with low surface tension (mixed water and ethanol 1:1 in volume) which reveals a flow speed of 0.6 m s(-1) (dropped from the height of 2 cm). All these features prove that adding another rough tier on a two-tier rough surface could futher improve its water-repellent properties.
authors.affiliation: Wuhan National Laboratory for Optoelectronics, and School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, 430074, People's Republic of China.
authors.forename: Yuanzhi
authors.initials: Y
authors.lastname: Cao
authors.forename: Longyan
authors.initials: L
authors.lastname: Yuan
authors.forename: Bin
authors.initials: B
authors.lastname: Hu
authors.forename: Jun
authors.initials: J
authors.lastname: Zhou