Nanoscale hydrophobic coatings for the separation of liquid mixtures

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Organofunctional nanoscale silane coatings are widely used to modify surface chemistry. Such coatings have many applications in micro- and nanofluidics because liquid motion on these scales is strongly influenced by capillary or wall effects. In this work we focus on the development of nanoscale coatings for chemically patterned surfaces using fluorosilane SAMs and fluorine containing methacrylate coatings for the novel approach to separate incompatible liquid mixtures on surfaces with an abrupt change of wettability from hydrophilic to hydrophobic. We aim for coatings easy to apply resulting in contact angles bigger 90° the same time being solvent resistant. Firstly we selectively deposit a fluorosilane by Chemical Vapor Deposition (CVD) at 70°C in the oven onto a silicon substrate by using patterned photoresist (UV-lithography) as a mask. Secondly we pattern the substrates by dipcoating the silicon substrates into a methacrylate solution for the formation of an hydrophobic polymer layer. The solvent resistance of these surfaces is investigated by exposing the substrate for 30min either to boiling Acetone or heated Toluene in an Ultrasonic bath at 65°C. Finally we demonstrate the possibility of separating Toluene/Water-mixtures on such surfaces with the following surface material combinations and contact angles θ: SiO2, 50°< θ< 54°/ Fluorosilane, 98°< θ< 110° (CVD, thin-film); SiO2, 50°< θ< 54° / Methacrylate-CP 95°< θ< 104° (dipcoating, thin-film).

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Journal: TechConnect Briefs
Volume: 4, Technical Proceedings of the 2007 NSTI Nanotechnology Conference and Trade Show, Volume 4
Published: May 20, 2007
Pages: 563 - 566
Industry sector: Advanced Materials & Manufacturing
Topics: Advanced Manufacturing, Nanoelectronics
ISBN: 1-4200-6376-6