Fabrication of PDMS micro/nano hybrid surface for increasing hydrophobicity

In this paper, we present a simple and low-cost fabrication method of PDMS (polydimethylsiloxane) micro/nano hybrid surfaces for the purpose of increasing hydrophobicity of a solid surface based on the PDMS replica molding using a photolithographically microstructured nanodimpled aluminum (MNA) master. To estimate the effect of micro/nano hybrid surfaces on the surface wettability, we have designed three geometry model surfaces consisting of: (1) a nanolens array, (2) a circular micropillar array, and (3) a micro/nano hybrid structure array (the nanolens array on top of the circular micropillar array). The MNA master was fabricated by combining the chemical oxidization of an aluminum substrate and UV-photolithography, thereby having a periodic microporous photoresist pattern on top of the nanodimpled aluminum surface. The micro/nano hybrid PDMS surface shows a higher contact angle compared with those of flat, nanopatterned and micropatterned PDMS surfaces. From the theoretical and experimental results, it was found that the nanotens array having a low aspect ratio of an intrinsically hydrophobic material enhances the hydrophobicity of the solid surface through increasing surface roughness within the Wenzel wetting mode. (C) 2009 Elsevier B.V. All rights reserved.