UVO-tunable superhydrophobic to superhydrophilic wetting transition on biomimetic nanostructured surfaces.
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).
Han
Joong Tark
JT
Polymers Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
Kim
Sangcheol
S
Karim
Alamgir
A
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
D011073:Polyamines; D014867:Water; C063994:polyallylamine; D010126:Ozone