Tavakoli Faryar, Kavehpour H Pirouz
Department of Mechanical and Aerospace Engineering, University of California, Los Angeles (UCLA) , Los Angeles, California 90024, United States.
Langmuir. 2015 Feb 24;31(7):2120-6. doi: 10.1021/la503620a. Epub 2015 Feb 9.
Superhydrophobic surfaces are characterized by their peculiarities, such as water-repellent, anti-icing, and freezing-delay properties. Wetting dynamics of deposited water drops on cooling hydrophobic surfaces, which directly affects the aforementioned properties, has not been studied thoroughly. Here, water drops are cooled on different hydrophobic surfaces in a controlled environment. During the cooling process, a significant increase in the drop footprint and decrease in the apparent contact angle are observed because of premature and capillary condensation, followed by thin water film formation adjacent to the solid-liquid-gas line. The water thin film propagates on the hydrophobic substrates radially away from the trijunction, followed by spreading of the drop on the film, which was experimentally validated through high-speed visualization. In addition, the roles of physical variables, such as the substrate temperature, humidity of surrounding air, types of hydrophobic surfaces, surface roughness, and drop volume, on post-spreading shape are investigated experimentally.
超疏水表面具有诸如防水、防冰和延迟结冰等特性。沉积在冷却疏水表面上的水滴的润湿动力学直接影响上述特性，但尚未得到充分研究。在此，在可控环境中，水滴在不同的疏水表面上冷却。在冷却过程中，由于过早的毛细凝聚，观察到液滴足迹显著增加，表观接触角减小，随后在固 - 液 - 气线附近形成薄水膜。水薄膜在疏水基底上从三相交界处径向向外传播，随后液滴在薄膜上扩散，这通过高速可视化实验得到了验证。此外，还通过实验研究了诸如基底温度、周围空气湿度、疏水表面类型、表面粗糙度和液滴体积等物理变量对液滴铺展后形状的影响。
