Yamada Yutaka, Ikuta Tatsuya, Nishiyama Takashi, Takahashi Koji, Takata Yasuyuki
Department of Aeronautics and Astronautics, Graduate School of Engineering, Kyushu University , Fukuoka 819-0395, Japan.
Langmuir. 2014 Dec 9;30(48):14532-7. doi: 10.1021/la503615a. Epub 2014 Nov 20.
Water condensation on a hybrid hydrophilic-hydrophobic 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 0.1-1.1 at 0.0 °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.
对亲水性-疏水性混合表面上的水凝结进行了研究，以揭示微观尺度下的成核机制。使用聚焦离子束（FIB）辐照以10纳米级的空间分辨率改变疏水表面的润湿性。利用环境扫描电子显微镜进行凝结实验；最小直径为800纳米的液滴排列在FIB辐照的亲水线上。扩展了非均相成核理论，以考虑被亲水区域吸引的水分子，从而能够解释不饱和条件下的成核机制。我们的结果表明，在0.0°C和560帕斯卡条件下，亲水区域上水分子的有效表面覆盖率为0.1 - 1.1，并且取决于FIB辐照的亲水线和疏水区域的宽度。这项工作中揭示的液滴成核机制将有助于设计具有增强滴状凝结传热性能的新表面。
