Stable superhydrophobic surfaces induced by dual-scale topography on SU-8

SU-8 is a photosensitive resist widely used for the fabrication of MEMS and lab-on-a-chip devices, as well as of model structures for testing wetting theories. In this work, superhydrophobic surfaces are fabricated on SU-8 by combining micro- and nano-sized structures formed by means of lithography and plasma etching, respectively. It is found that nanotexturing of the micropatterned SU-8 surfaces is essential in enhancing surface hydrophobicity and rendering the surfaces water repellent (i.e. minimizing contact angle hysteresis). The proposed method will be shown to be of paramount importance for the fabrication of mechanically stable and robust superhydrophobic SU-8 surfaces with low aspect ratio microstructuring.