Fabrication of superhydrophobic surfaces on flexible fluorinated foils by using dual-scale patterning

This paper investigates the interest of combining NanoImprint Lithography with plasma treatment in order to easily create dual-scale superhydrophobic surfaces on flexible fluorinated foils. The studies were led on FEP and PCTFE materials with conditions compatible with standard NIL equipments. Different pattern geometries, densities and aspect ratio have been investigated and we show that patterning at a nanometer scale improves hydrophobic behaviour compared to microstructuration. Water-contact angle (WCA) of 154° (and water contact angle hysteresis of 11 ± 2°) were measured, which corresponds to a superhydrophobic surface. However, patterning large surfaces at nanoscale with a high aspect ratio is more difficult to achieve and limits the use of such a process for industrial applications. So, we have decided to induce a nanopatterning on microstructures previously printed using plasma etching. This plasma roughening leads to a highly superhydrophobic surface and WCA values as high as 170°.