Fabrication of hydrophobic and anti-reflective polymeric films using anodic aluminum-oxide imprints

Abstract

A simple and cost effective method to fabricate anti-reflective (AR) and hydrophobic (HP) polymeric films was attempted by developing micro-, nano- and micro/nano-porous Al/ anodic aluminum oxide (AAO) imprinting molds and then replicating the surface morphology of the molds on poly methyl methacrylate (PMMA) and polycarbonate (PC) polymeric films by using thermal nanoimprint lithography (NIL). A micro-porous structure was fabricated by using UV-light lithography followed by etching, and a nano-porous structure using repetitions of anodizing and subsequent etching. As a result, micro-, nano- and micro/nano-porous Al/AAO imprints and micro-, nanoand micro/nano-pillared PMMA and PC replica films in which the pores and the pillars were uniformly well-arranged in a hexagonal array, were successfully fabricated. An AR and HP PMMA replica film with an array of nano-pillars revealing a transmittance of 94.3% and a water contact angle (WCA) of 124°, could be fabricated. By incorporating nano-pillars on a micro-pillared structure, the WCA of the PC film was increased from 128 to 143°, but that of the PMMA film remained almost the same. The incorporation of the smooth micro-pillar structure on both the bare and the nano-pillared PMMA and PC films was found to reduce significantly the visible light transmittance, but a high transmittance was found only in the nano-pillared films.