Fabrication of anisotropic super hydrophobic/hydrophilic nanoporous membranes by plasma polymerization of C4F8 on anodic aluminum oxide

Freestanding anodic aluminum oxide (AAO) membranes were fabricated using a two-step anodization procedure, voltage reduction method, and inductively coupled plasma polymerization. The fabrication process was monitored with electrochemical and spectroscopic ellipsometry measurements, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy. Static contact angle measurements demonstrated that the two surfaces of the fabricated AAO membranes have dramatically different degrees of hydrophobicity. The contact angle of water on the side modified with the fluorocarbon film was 150degrees, whereas the contact angle on the hydrophilic side, which was initially attached to the aluminum substrate, was less than 5degrees. The fabricated freestanding AAO membranes with only one hydrophobic surface are expected to find applications in the design of new systems for separation and filtration and as gas and liquid transport devices such as gas-diffusion electrodes for miniature power sources and sensors. (C) 2004 The Electrochemical Society.