One-Step Process for Superhydrophobic Metallic Surfaces by Wire Electrical Discharge Machining
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- 作者：Won Gyu Bae ; Ki Young Song ; Yudi Rahmawan ; Chong Nam Chu ; Dookon Kim ; Do Kwan Chung ; Kahp Y. Suh
- 刊名：ACS Applied Materials & Interfaces
- 出版年：2012
- 出版时间：July 25, 2012
- 年：2012
- 卷：4
- 期：7
- 页码：3685-3691
- 全文大小：500K
- 年卷期：v.4,no.7(July 25, 2012)
- ISSN：1944-8252
文摘
We present a direct one-step method to fabricate dual-scale superhydrophobic metallic surfaces using wire electrical discharge machining (WEDM). A dual-scale structure was spontaneously formed by the nature of exfoliation characteristic of Al 7075 alloy surface during WEDM process. A primary microscale sinusoidal pattern was formed via a programmed WEDM process, with the wavelength in the range of 200 to 500 渭m. Notably, a secondary roughness in the form of microcraters (average roughness, Ra: 4.16 to 0.41 渭m) was generated during the exfoliation process without additional chemical treatment. The low surface energy of Al 7075 alloy (纬 = 30.65 mJ/m2) together with the presence of dual-scale structures appears to contribute to the observed superhydrophobicity with a static contact angle of 156掳 and a hysteresis less than 3掳. To explain the wetting characteristics on dual-scale structures, we used a simple theoretical model. It was found that Cassie state is likely to present on the secondary roughness in all fabricated surfaces. On the other hand, either Wenzel or Cassie state can present on the primary roughness depending on the characteristic length of sinusoidal pattern. In an optimal condition of the serial cutting steps with applied powers of 30 and 8 kW, respectively, a stable, superhydrophobic metallic surface was created with a sinusoidal pattern of 500 渭m wavelength.