Atmospheric rf plasma deposition of superhydrophobic coatings using tetramethylsilane precursor

Significance statement

Superhydrophobic surfaces have very low surface energy, so water or other liquids in contact with the surface tend to bead up and roll off very easily. Superhydrophobic coatings are therefore useful in a wide variety of applications, such as self-cleaning glass for windshields, windows, or solar panels, stain-resistant and self-cleaning fabrics, and low friction coatings. But the primary difficulty in using superhydrophobic coatings is that they tend to be extremely fragile and wear away very quickly. In a previous publication, we showed that a superhydrophobic coating could be created quickly and easily using plasma deposition with a feed of simple organic compounds. However, those coatings were so fragile that they could be quickly rubbed away. In this follow-up work, we show that using tetramethylsilane in the feed instead of hydrocarbons leads to much more durable coatings without any loss in superhydrophobicity. The durability comes because the silicon in the feed creates inorganic-organic-hybrid bonds in the coating that are stronger than either inorganic or organic bonds alone. These coatings can be applied to almost any surface, including metals, glass, or paper, and require no surface pre-treatments, so this method could be useful for improving various manufactured products.

Figure Legend: Many small water droplets scattered on a piece of aluminum with a superhydrophobic coating.

Journal Reference

Surface and Coatings Technology, Volume 234, 15 November 2013, Pages 14–20.

David J. Marchanda, Zachary R. Dilwortha, Robert J. Stauffera, Erik Hsiaoa, Jeong-Hoon Kimb, Jung-Gu Kangb, Seong H. Kima.

^a Department of Chemical Engineering and Materials Research Institute, The Pennsylvania State University, University Park, PA 16802, USA and

^b SPS Co., Ltd., #305 Sinwoo Plaza, 83 Banwol-dong, Hwaseong-Si, Gyeonggi-do, 445-330, South Korea.

Abstract

Non-fluorine-based organic–inorganic-hybrid coatings exhibiting superhydrophobic properties were prepared using a single-step process of atmospheric rf glow discharge plasma deposition with a tetramethylsilane (TMS) precursor. The plasma was generated with He in air and the TMS precursor concentration was 0.01–0.04 vol.% of the He carrier gas. The dissociation of TMS in the atmospheric plasma accompanied the formation of particulates through gas-phase condensation reactions, which lead to organic–inorganic-hybrid coatings with a root-mean-squared roughness in the ~ 30–80 nm range and a water contact angle of ~ 150°–165° on a variety of substrates including flat wafers, papers, and cotton fabric without any sample pre-treatments. Due to the excitation and dissociation of ambient molecules (oxygen, nitrogen, and water) in the atmospheric plasma, the produced coatings contained oxygen and nitrogen, in addition to silicon and hydrocarbon groups. The oxygen species in the film appears to be a part of Si–O–Si networks similar to silicone compounds. The films produced with TMS exhibited an improved environmental durability compared to purely hydrocarbon-based films deposited with the same atmospheric plasma process.

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Atmospheric rf plasma deposition of superhydrophobic coatings using tetramethylsilane precursor

Abstract

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