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Bioinspired Durable Superhydrophobic Surface from a Hierarchically Wrinkled Nanoporous Polymer

Chen, Ting-Lun, Huang, Ching-Yu, Xie, Yi-Ting, Chiang, Ya-Yu, Chen, Yen-Ming, Hsueh, Han-Yu
ACS applied materials & interfaces 2019 v.11 no.43 pp. 40875-40885
adhesion, chemical composition, contact angle, heat treatment, hydrophobicity, nanopores, perfluorocarbons, polystyrenes, surfactants
Inspired by complex multifunctional leaves, in this study, we created robust hierarchically wrinkled nanoporous polytetrafluoroethene (PTFE) surfaces that exhibit superhydrophobic properties by combination of PTFE micellization and spontaneous surface wrinkling on a commercially available thermoretractable polystyrene (PS) sheet. A PTFE dispersion was coated onto the PS sheet, followed by thermal treatment to remove the surfactants surrounding the PTFE particles, and surface wrinkling was induced through a dynamic thermal contraction process. Thermally induced contraction from the PS sheet provided the driving force for developing and stabilizing micrometer-sized wrinkle formation, whereas the nanometer-sized PTFE particle aggregation formed a rigid nanoporous film, providing its intrinsic hydrophobic character. By combining the hierarchical interfacial structure and chemical composition, hierarchically wrinkled nanoporous PTFE surfaces were fabricated, which exhibited extremely high water repellence (water contact angle of ∼167°) and a water rolling-off angle lower than 5°. The wrinkled patterns could intimately bind the nanoporous PTFE layer through enhanced adhesion from their curved surface and viscous liquid surfactants, making these surfaces mechanically robust and offering potentially extendable alternatives with self-cleaning, antifouling, and drag-reducing properties.