Droplet Nucleation on a Well-Defined Hydrophilic鈥揌ydrophobic Surface of 10 nm Order Resolution

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• 作者：Yutaka Yamada ; Tatsuya Ikuta ; Takashi Nishiyama ; Koji Takahashi ; Yasuyuki Takata
• 刊名：Langmuir
• 出版年：2014
• 出版时间：December 9, 2014
• 年：2014
• 卷：30
• 期：48
• 页码：14532-14537
• 全文大小：387K
• ISSN：1520-5827

文摘

Water condensation on a hybrid hydrophilic鈥揾ydrophobic surface was investigated to reveal nucleation mechanisms at the microscale. Focused ion beam (FIB) irradiation was used to change the wettability of the hydrophobic surface with 10 nm order spatial resolution. Condensation experiments were conducted using environmental scanning electron microscopy; droplets, with a minimum diameter of 800 nm, lined up on the FIB-irradiated hydrophilic lines. The heterogeneous nucleation theory was extended to consider the water molecules attracted to the hydrophilic area, thereby enabling explanation of the nucleation mechanism under unsaturated conditions. Our results showed that the effective surface coverage of the water molecules on the hydrophilic region was 0.1鈥?.1 at 0.0 掳C and 560 Pa and was dependent on the width of the FIB-irradiated hydrophilic lines and hydrophobic area. The droplet nucleation mechanism unveiled in this work would enable the design of new surfaces with enhanced dropwise condensation heat transfer.