Bouncing Regimes of Supercooled Water Droplets Impacting Superhydrophobic Surfaces with Controlled Temperature and Humidity.
Bouncing Regimes of Supercooled Water Droplets Impacting Superhydrophobic Surfaces with Controlled Temperature and Humidity.
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DOI：
10.1021/acs.langmuir.3c01099
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发表时间：
2023-07
期刊：
影响因子：
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通讯作者：
Chunfang Guo;Lei Liu;Rui Yang;Jiangtao Lu;Senyun Liu
中科院分区：
文献类型：
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作者：
Chunfang Guo;Lei Liu;Rui Yang;Jiangtao Lu;Senyun Liu
超疏水表面由于其独特的拒水性在被动防冰应用中显示出巨大的潜力。减少撞击液滴与具有某些纹理的下层表面之间的接触时间，特别是应用薄煎饼弹跳机制，预期可消除撞击时的液滴结冰。然而，这种超疏水表面对过冷水滴的影响的防冰性能尚未被研究。因此，我们制备了一种典型的阵列后超疏水表面（PSHS）和一种平坦的超疏水表面（FSHS），研究了温度和湿度控制下液滴在其上的撞击动力学。系统地研究了这些表面上的接触时间和弹跳行为及其对表面温度、韦伯数和表面结霜的依赖性。在FSHS上观察到常规的回弹和完全粘附，并且粘附主要由液滴渗透到表面微/纳米结构中以及随后的Cassie-to-Wenzel转变引起。在PSHS上，观察到四种不同的区域，包括煎饼反弹、常规反弹、部分反弹和完全粘附，其中接触时间相应地增加。在一定的韦伯数范围内，煎饼反弹制度，其中液滴反弹的表面与一个显着缩短的接触时间有利于防冰性能。通过进一步降低表面温度，饼状回弹变成常规回弹，其中液滴在毛细管排空过程之后不悬浮。我们的规模分析表明，霜之间的职位减少了毛细血管能量储存在向下渗透，导致失败的煎饼反弹。由于液滴成核和润湿转变的耦合作用，在足够低的温度下，尤其是在较大的韦伯数下，液滴粘附在结霜表面上。
Superhydrophobic surfaces have shown significant potential for the passive anti-icing application due to their unique water repellency. Reducing the contact time between the impacting droplets and the underlying surfaces with certain textures, especially applying the pancake bouncing mechanism, is expected to eliminate droplet icing upon impingement. However, the anti-icing performance of such superhydrophobic surfaces against the impact of supercooled water droplets has not yet been examined. Therefore, we fabricated a typical post-array superhydrophobic surface (PSHS) and a flat superhydrophobic surface (FSHS), to study the droplet impact dynamics on them with controlled temperature and humidity. The contact time and the bouncing behavior on these surfaces and their dependence on the surface temperature, Weber number, and surface frost were systematically investigated. The conventional rebound and full adhesion were observed on the FSHS, and the adhesion is mainly induced by the penetration of the droplet into the surface micro/nanostructures and the consequent Cassie-to-Wenzel transition. On the PSHS, four distinct regimes including pancake rebound, conventional rebound, partial rebound, and full adhesion were observed, where the contact time increases correspondingly. Over a certain Weber number range, the pancake rebound regime where the droplet bounces off the surface with a dramatically shortened contact time benefits the anti-icing performance. By further decreasing the surface temperature, the pancake rebound turns into the conventional rebound, where the droplet is not levitated after the capillary emptying process. Our scale analysis indicates that the frost between the posts reduces the capillary energy stored during the downward penetration, resulting in the failure of the pancake bouncing. A droplet adheres onto the frosted surface at sufficiently low temperature, especially at larger Weber numbers, on account of the coupling influence of droplet nucleation and wetting transition.