Facile one-step fabrication of super-repellent nanoporous anodic alumina using a non-fluorinated approach

Inspired by lotus-effect, superhydrophobicity has attracted considerable interest in various areas such as self-cleaning, antifouling and liquid transportation, and so on. Superhydrophobic surfaces can be prepared mostly by altering the surface with creating micro/nanoscale structures or with chemically modifying by materials of low surface energy. In this study, the electrochemically fabricated nanoporous alumina is deposited with poly(dimethylsiloxane) via a one-step thermal treatment to achieve ultra-water repellent or superhydrophobic surfaces. Nanoporous anodic alumina substrates with varying pore diameters were used for the poly(dimethylsiloxane) deposition, and their morphological characterization is carried out using the field emission scanning electron microscope. Energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy inferred the chemical composition, while contact angle measurements using a commercial contact angle measurement system is exploited to probe the water spreading behaviour on the fabricated substrates. The substrates also exhibit high repellence behaviour towards ethylene glycol. The superhydrophobic behaviour of the fabricated substrates is investigated while the substrate is immersed in organic solvents like decane, hexane and toluene. In addition, the super repellence behaviour of the substrates against the corrosive chemicals such as aqua regia and saturated sodium hydroxide is investigated and the substrate was found to retain its super repellence behaviour against corrosive solutions. Further, the self-cleaning properties and antifouling behaviour of the fabricated substrates were also demonstrated.