title: Hydrophobicity and freezing of a water droplet on fluoroalkylsilane coatings with different roughnesses.
abstract: Smooth (Ra approximately 0.1 nm) and rough (Ra approximately 20 nm) coatings of 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (FAS-17) were prepared by controlling process conditions. The water contact angles for the smooth and rough coatings were similar (107 degrees and 110 degrees, respectively), but their sliding angles differed considerably (10 degrees and 27 degrees, respectively). The surface potential on the smooth coating, assessed using Kelvin force microscopy, showed a sharp distribution, but that on the rough coating ranged widely, implying large chemical heterogeneity including residual SiOH groups. The freezing temperature of a supercooled water droplet on the rough coating was higher than that on the smooth coating.
authors.affiliation: Department of Metallurgy and Ceramic Science, Graduate School of Science and Engineering, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8552, Japan.
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Suzuki
authors.forename: Akira
authors.initials: A
authors.lastname: Nakajima
authors.forename: Naoya
authors.initials: N
authors.lastname: Yoshida
authors.forename: Munetoshi
authors.initials: M
authors.lastname: Sakai
authors.forename: Ayako
authors.initials: A
authors.lastname: Hashimoto
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Kameshima
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Okada