Abstract
This work reports on an electrochemical system which allows the control of surface wettability properties by voltage induced changes in contact angle (Theta) of Delta Theta >= 50 degrees. For this we used conductive TiO2 nanotubular layers that were modified with ferrocene coupled to the TiO2 surface via triethoxysilane. To enhance the hydrophobic character of the nanotubular TiO2 surface, also mixed organic monolayers; namely perfluorotriethoxysilane, were explored. Formation of the ferrocene and mixed organic monolayer was confirmed by X-ray-photoelectron-spectroscopy (XPS). Contact angle combined with electrochemical measurements show that ferrocene in these monolayers; can successfully be switched from Fe2+ to Fe3+ and that this change in the redox state considerably alters the wetting properties. Using a conductive nanotube substrate allows us to amplify this change by a factor of more than 10, and thus this surface can be used to trigger significant wetting alterations. (C) 2009 Elsevier B.V. All rights reserved.