title: Nonfunctionalized polydimethyl siloxane superhydrophobic surfaces based on hydrophobic-hydrophilic interactions.
abstract: Superhydrophobic surfaces based on polydimethyl siloxane (PDMS) were fabricated using a 50:50 PDMS-poly(ethylene glycol) (PEG) blend. PDMS was mixed with PEG, and incomplete phase separation yielded a hierarchic structure. The phase-separated mixture was annealed at a temperature close to the crystallization temperature of the PEG. The PEG crystals were formed isothermally at the PDMS/PEG interface, leading to an engineered surface with PDMS spherulites. The resulting roughness of the surface was studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The PDMS spherulites, a few micrometers in diameter observed from SEM images, were found to have an undulated (rippled) surface with nanometer-sized features. The combination of micrometer- and nanometer-sized surface features created a fractal surface and increased the water contact angle (WCA) of PDMS more than 60°, resulting in a superhydrophobic PDMS surface with WCA of >160°. The active surface layer for the superhydrophobicity was approximately 100 μm thick, illustrating that the material had bulk superhydrophobicity compared to conventional fluorocarbon or fluorinated coated rough surfaces. Theoretical analysis of the fractal surface indicates that the constructed surface has a fractal dimension of 2.5, which corresponds to the Apollonian sphere packing.
authors.affiliation: Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
authors.forename: Georgios
authors.initials: G
authors.lastname: Polizos
authors.forename: Enis
authors.initials: E
authors.lastname: Tuncer
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Qiu
authors.forename: Tolga
authors.initials: T
authors.lastname: Aytuǧ
authors.forename: Michelle K
authors.initials: MK
authors.lastname: Kidder
authors.forename: Jamie M
authors.initials: JM
authors.lastname: Messman
authors.forename: Isidor
authors.initials: I
authors.lastname: Sauers