title: Micro-micro hierarchy replacing micro-nano hierarchy: a precisely controlled way to produce wear-resistant superhydrophobic polymer surfaces.
abstract: Superhydrophobic polymer surfaces are typically fabricated by combining hierarchical micro-nanostructures. The surfaces have a great technological potential because of their special water-repellent and self-cleaning properties. However, the poor mechanical robustness of such surfaces has severely limited their use in practical applications. This study presents a simple and swift mass production method for manufacturing hierarchically structured polymer surfaces at micrometer scale. Polypropylene surface structuring was done using injection molding, where the microstructured molds were made with a microworking robot. The effect of the micro-microstructuring on the polymer surface wettability and mechanical robustness was studied and compared to the corresponding properties of micro-nanostructured surfaces. The static contact angles of the micro-microstructured surfaces were greater than 150° and the contact angle hysteresis was low, showing that the effect of hierarchy on the surface wetting properties works equally well at micrometer scale. Hierarchically micro-microstructured polymer surfaces exhibited the same superhydrophobic wetting properties as did the hierarchically micro-nanostructured surfaces. Micro-microstructures had superior mechanical robustness in wear tests as compared to the micro-nanostructured surfaces. The new microstructuring technique offers a precisely controlled way to produce superhydrophobic wetting properties to injection moldable polymers with sufficiently high intrinsic hydrophobicity.
authors.affiliation: Department of Chemistry, University of Eastern Finland, P.O. Box 111, FI-80101, Joensuu, Finland.
authors.forename: Eero
authors.initials: E
authors.lastname: Huovinen
authors.forename: Janne
authors.initials: J
authors.lastname: Hirvi
authors.forename: Mika
authors.initials: M
authors.lastname: Suvanto
authors.forename: Tapani A
authors.initials: TA
authors.lastname: Pakkanen
mesh_terms: D057927:Hydrophobic and Hydrophilic Interactions; D049329:Nanostructures / Q000737:chemistry*; D010316:Particle Size; D011126:Polypropylenes / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D011126:Polypropylenes