Bio-inspired water repellent surfaces produced by ultrafast laser structuring of silicon

We report here an efficient method for preparing stable superhydrophobic and highly water repellent surfaces by irradiating silicon wafers with femtosecond laser pulses and subsequently coating them with chloroalkylsilane monolayers. By varying the laser pulse fluence on the surface one can successfully control its wetting properties via a systematic and reproducible variation of roughness at micro- and nano-scale, which mimics the topology of natural superhydrophobic surfaces. The self-cleaning and water repellent properties of these artificial surfaces are investigated. It is found that the processed surfaces are among the most water repellent surfaces ever reported. These results may pave the way for the implementation of laser surface microstructuring techniques for the fabrication of superhydrophobic and self-cleaning surfaces in different kinds of materials as well. (C) 2008 Elsevier B. V. All rights reserved.