Superhydrophobic Thermoplastic Surfaces with Hierarchical Micro-Nanostructures Fabricated by Hot-Embossing

Hierarchical micro-nanostructures comprising nanopillars superimposed onto micropillars were successfully fabricated over larger areas on thermoplastic cyclic olefin polymer (COP) substrates. Both the nanostructures (100 nm to 500 nm diameter) and microstructures (14–20 µm diameter) were hot-embossed monolithically using an intermediate fluorinated polymer mold replicated from a Si master. The as-fabricated thermoplastic hierarchical micro-nanopillar surfaces are superhydrophobic with advancing contact angles greater than 150°. Superhydrophobic surfaces with static contact angle as large as 167° were achieved on COP substrates using nanopillars as small as 150 nm and following post-fabrication fluorocarbon coating. The sliding angle of a water drop on the superhydrophobic surface is 2.5°.