title: UVO-tunable superhydrophobic to superhydrophilic wetting transition on biomimetic nanostructured surfaces.
abstract: A novel strategy for a tunable sigmoidal wetting transition from superhydrophobicity to superhydrophilicity on a continuous nanostructured hybrid film via gradient UV-ozone (UVO) exposure is presented. Along a single wetting gradient surface (40 mm), we could visualize the superhydrophobic (thetaH2O > 165 degrees and low contact angle hysteresis) transition (165 degrees > thetaH2O > 10 degrees ) and superhydrophilic (thetaH2O < 10 degrees within 1 s) regions simply through the optical images of water droplets on the surface. The film is prepared through layer-by-layer assembly of negatively charged silica nanoparticles (11 nm) and positively charged poly(allylamine hydrochloride) with an initial deposition in a fractal manner. The extraordinary wetting transition on chemically modified nanoparticle layered surfaces with submicrometer- to micrometer-scale pores represents a competition between the chemical wettability and hierarchical roughness of surfaces as often occurs in nature (e.g., lotus leaves, insect wings, etc).
authors.affiliation: Polymers Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
authors.forename: Joong Tark
authors.initials: JT
authors.lastname: Han
authors.forename: Sangcheol
authors.initials: S
authors.lastname: Kim
authors.forename: Alamgir
authors.initials: A
authors.lastname: Karim
mesh_terms: D032701:Biomimetics; D002627:Chemistry, Physical / Q000379:methods*; D017709:Fractals; D005898:Glass; D008855:Microscopy, Electron, Scanning; D053758:Nanoparticles / Q000737:chemistry*; D010126:Ozone; D010316:Particle Size; D011073:Polyamines / Q000737:chemistry; D013499:Surface Properties; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry; D017155:Wettability
chemical_list: D011073:Polyamines; D014867:Water; C063994:polyallylamine; D010126:Ozone