Hindawi Publishing Corporation Journal of Nanotechnology Volume 2011, Article ID 392754, 6 pages doi:10.1155/2011/392754 Research Article Improving the Hydrophobicity of ZnO by PTFE Incorporation Meenu Srivastava, Bharathi Bai J. Basu, and K. S. Rajam Council of Scientific and Industrial Research, Surface Engineering Division, National Aerospace Laboratories, Bangalore 560 017, India Correspondence should be addressed to Meenu Srivastava, meenu srivas@yahoo.co.uk Received 7 March 2011; Accepted 24 March 2011 Academic Editor: Mallikarjuna Nadagouda Copyright © 2011 Meenu Srivastava et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The objective of the present study is to obtain a zinc oxide- (ZnO-) based superhydrophobic surface in a simple and cost-effective manner. Chemical immersion deposition being simple and economical has been adopted to develop modified ZnO coating on glass substrate. Several modifications of ZnO like treatment with alkanoic acid (stearic acid) and fluoroalkylsilane to tune the surface wettability (hydrophobicity) were attempted. The effect of thermal treatment on the hydrophobic performance was also studied. It was observed that thermal treatment at 70 ◦ C for 16 hrs followed by immersion in stearic acid resulted in high water contact angle (WCA), that is, a superhydrophobic surface. Thus, a modified ZnO superhydrophobic surface involves the consumption of large amount of electrical energy and time. Hence, the alternate involved the incorporation of low surface energy fluoropolymer polytetrafluoroethylene (PTFE) in the ZnO coating. The immersion deposited ZnO-PTFE composite coating on modification with either stearic acid or fluoroalkylsilane resulted in a better superhydrophobic surface. The coatings were characterized using Scanning Electron Microscope (SEM) for the surface morphology. It was found that microstructure of the coating was influenced by the additives employed. A flower-like morphology comprising of needle-like structure arranged in a radial manner was exhibited by the superhydrophobic coating. 1. Introduction Superhydrophobic surfaces (water contact angle >150 ◦ ) are gaining importance in industrial applications and academia due to their unique properties like self-cleaning, deicing, antisticking, and anticontamination. Some of the applica- tions include self-cleaning paints, transparent antireflective coatings, self-cleaning glass, and wiperless windshields. In recent times, their usage in aerospace sector is also being explored, particularly in the tail and wings of the aircraft to reduce drag and thereby improve the efficiency of the engine. Superhydrophobicity can be achieved by obtaining a surface of micro- to nanoscale architecture [1]. Empirical models have been proposed on the basis of experimental data to explain the surface wetting properties and to understand the phenomenon of superhydrophobicity. Interest in this phenomenon increased in 1997 when the origin and the universal principle of “Lotus Effect” in nature were explained by Zhang et al. [1]. Since then, research has been focused on mimicking nature and trying to fabricate such surfaces artificially. Various methods have been recommended for the fabri- cation of such a surface. Broadly, they have been classified as top-down approach, bottom-up approach, and a combined approach. Solution immersion process, which is a bottom- up method, has been adopted in the present study. The advantage of this method is that it is simple, economical and can be easily scaled up for large area applications. ZnO has been chosen because of its antimicrobial property, easy availability, and nontoxic nature [2]. Also it has other properties like photocatalytic ability, electrical conductivity, UV absorption, and photo-oxidizing capacity for chemical and biological species. Very recently, preparation of cotton bandages with antibacterial properties by immobilizing ZnO nanoparticles on the fabric surface has been reported [3]. Considerable work has been carried out on the immersion deposition of ZnO [4–12]. Shinde et al. have reported the structure, optical and electrical properties of heat-treated ZnO [4]. Similar aspect of Sr-doped ZnO film has also been studied [5]. The effect of thermal desorption of stearic acid on the superhydrophobic performance of ZnO has been reported by Saleema and Farzaneh [6]. ZnO nanorods have