A replication strategy for complex micro/nanostructures with superhydrophobicity and superoleophobicity and high contrast adhesion

Abstract

The present work reports a replication approach to imprint complex micro/nanostructures into polymeric coatings and materials, such as silicone elastomers, polyurethane, ultra-high-molecular-weight polyethylene and polytetrafluoroethylene etc., with applications in engineering. Al and Al₂O₃ molds with terraced micro/nanostructures were produced using an industrially compatible anodization method. To assist replication, the molds were coated with a water-soluble polymer layer as the sacrificial layer, to reduce the adhesion between replica and mold. Polymeric replicas with complex terraced structures were successfully obtained, which were otherwise impossible to achieve with conventional perfluorinated molds. The as-prepared replicas all exhibited superhydrophobicity without further modification with low-surface-energy coatings. Interestingly, residual hydrophilic sacrificial layer resulted in high water-adhesion without losing superhydrophobicity; these surfaces turned extremely slippery after removal of the residual sacrificial layer. A molecular mechanism is proposed to interpret the contrast adhesion. After being coated with a sticky perfluoroalkyl, containing methacrylate, the surfaces convert to superoleophobicity and low adhesion to a number of oils.