Surface modified nano-patterned SU-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 mu m 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 degrees-5 degrees. 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 degrees. 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.