Fabrication of nano-periodic structure for water repellent using femtosecond laser

The lotus has been a symbol of extreme water-repellent (superhydrophobicity) characterized by a high contact angle and low sliding angle. We demonstrate a methodology to fabricate a three-dimensional (3-D) nano-periodic structure on a thin plastic film in an attempt to process a superhydrophobic surface. The whole fabrication process was carried out in two steps:(i) writing a nano-periodic 3-D pattern on a metal (mold) surface by focused femtosecond (fs) laser pulses and (ii) transferring the 3-D pattern from the mold to a plastic film by hot embossing. This technique allows the fabrication of nano-periodic structure as small as 800 nm pitch. The contact angles were improved on both the surfaces of the metal mold and the plastic film.