Surface modified nano-patternedSU-8 pillar array optically transparent super-hydrophobic thin film

We report the fabrication and characterization of a porous nano-patterned SU -8 high aspect ratio pillar array as a transparent super-hydrophobic thin film. A 250 µm thick SU -8 layer was backside exposed through a glass substrate to form an array of high aspect ratio tapered pillars with angles in the range of 3°–5°. The SU -8 pillar array was plasma treated to form nano-porous surfaces, and then subsequently coated with fluorocarbon (FC) or Parylene-C film. Static contact angles and optical transmittance of various surface conditions such as with and without plasma treatment, Parylene-C versus FC, were tested and results were compared. Among various surface treated SU -8 pillar arrays, the plasma-treated nano-porous FC-coated SU -8 pillar array showed the highest static contact angle of 161°. It was found that the optical transmittance at around 530 nm for the nano-porous FC-coated SU -8 pillar array was approximately 65%, while the bare SU -8 film was approximately 95%. These nano-patterned transparent polymer films could be used in various water-repellent applications.