Roll-to-roll fabrication of hierarchical superhydrophobic surfaces

Abstract

In this letter, we report a roll-to-roll fabrication method to develop a hierarchical nanopatterned superhydrophobic surface. The hierarchical pattern includes a primary micropattern with an overlayed secondary nanopattern. The primary pattern of 15–30 μm length scales was fabricated through UV nanoimprint lithography. The secondary nanopattern of 20 nm size was generated through a subsequent scalable spray coating with hydrophobic silica nanoparticles to create a nanoscale random roughness over the primary pattern. The secondary nanocoating over the primary pattern resulted in an enhanced contact angle resulting in superhydrophobicity and reduced hysteresis. Freezing droplet measurements performed have demonstrated a fivefold increase in the time for the droplet to freeze on a superhydrophobic surface compared to a primary hydrophobic structure.