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Coatings 2018, 8(7), 227; https://doi.org/10.3390/coatings8070227

Hot Embossing for Whole Teflon Superhydrophobic Surfaces

1
Institute of Robotics and Automatic Information System & Tianjin Key Laboratory of Intelligent Robotics, Nankai University, Tianjin 300071, China
2
Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ 07030, USA
*
Author to whom correspondence should be addressed.
Received: 30 May 2018 / Revised: 16 June 2018 / Accepted: 16 June 2018 / Published: 22 June 2018
(This article belongs to the Special Issue Superhydrophobic Coatings)
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Abstract

In this paper, we report a simple fabrication process of whole Teflon superhydrophobic surfaces, featuring high-aspect-ratio (>20) nanowire structures, using a hot embossing process. An anodic aluminum oxide (AAO) membrane is used as the embossing mold for the fabrication of high-aspect-ratio nanowires directly on a Teflon substrate. First, high-aspect-ratio nanowire structures of Teflon are formed by pressing a fluorinated ethylene propylene (FEP) sheet onto a heated AAO membrane at 340 °C, which is above the melting point of FEP. Experimental results show that the heating time and aspect ratios of nanopores in the AAO mold are critical to the fidelity of the hot embossed nanowire structures. It has also been found that during the de-molding step, a large adhesive force between the AAO mold and the molded FEP greatly prolongs the length of nanowires. Contact angle measurements indicate that Teflon nanowires make the surface superhydrophobic. The reliability and robustness of superhydrophobicity is verified by a long-term (~6.5 h) underwater turbulent channel flow test. After the first step of hot-embossing the Teflon nanowires, microstructures are further superimposed by repeating the hot embossing process, but this time with microstructured silicon substrates as micromolds and at a temperature lower than the melting temperature of the FEP. The results indicate that the hot embossing process is also an effective way to fabricate hierarchical micro/nanostructures of whole Teflon, which can be useful for applications of Teflon material, such as superhydrophobic surfaces. View Full-Text
Keywords: Teflon; hot embossing; nanowire; superhydrophobic surface Teflon; hot embossing; nanowire; superhydrophobic surface
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Li, J.; Yu, W.; Zheng, D.; Zhao, X.; Choi, C.-H.; Sun, G. Hot Embossing for Whole Teflon Superhydrophobic Surfaces. Coatings 2018, 8, 227.

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