Superhydrophobic surfaces engineered using diatomaceous earth

We present a simple method to prepare superhydrophobic surfaces using siliceous exoskeleton of diatoms, a widespread group of algae. This makes diatomaceous earth an accessible and cheap natural material. A micro/nanoscale hierarchical topography was achieved by coating a glass surface with diatomaceous earth, giving rise to a superhydrophilic surface. Superhydrophobic surfaces were obtained by a further surface chemical modification through fluorosilanization. The wettability of the superhydrophobic surface can be modified by Argon plasma treatment in a controlled way by exposure time variation. The chemical surface modification by fluorosilanization and posterior fluorinated SH surface modification by plasma treatment was analyzed by XPS. Using appropriated hollowed masks only specific areas on the surface were exposed to plasma permitting to pattern hydrophilic features with different geometries on the superhydrophobic surface. We showed that the present strategy can be also applied in other substrates, including thermoplastics, enlarging the potential applicability of the resulting surfaces.This work was carried out under the scope of the EU 7th Framework Programme (FP7/2007-2013) under grant agreement no. FP7-KBBE-2010-4-266033 (SPECIAL). N.M.O. acknowledge the Portuguese Foundation for Science and Technology (FCT) for his PhD scholarship (SFRH/BD/73172/2010). The authors wish to thank Dr. Carmen Serra from CACTI of the University of Vigo for the XPS measurements and optical profilometry analysis