Investigation of the dew condensation and subsequent spontaneous jumping of droplets on the highly hydrophobic surface under cooling

以薄水铝石和疏水硅烷为原料，制备了具有纳米级随机粗糙度结构的超疏水涂层。样品用Peltier冷却元件冷却，利用高速摄像系统从两个不同的方向观察到露水凝结在涂层上形成的水滴的自发跳跃。水滴的自发跳跃发生在两个以上的水滴合并、变形和形状恢复之后。小的跳跃液滴表现出较大的初始跳跃速度。初始跳跃速度随聚并前液滴尺寸差的增大而减小。实际跳跃速度小于理论值。当样品下降到30度时，水滴的跳跃频率随着冷却时间和持续液滴去除性能的变化重复着递增-递减循环。在外加电场的作用下，水滴的跳跃高度显著增加。

Superhydrophobic coatings with nano-scale random roughness structure were prepared using boehmite and hydrophobic silanes. The samples were cooled by Peltier cooling element, and spontaneous jumping of water droplets formed on the coatings by dew condensation was observed from two different directions using high-speed camera systems. Spontaneous jumping of water droplets occurred subsequent to coalescence of more than two water droplets, deformation, and shape recovery. Small jumping droplets exhibited great initial jumping velocity. Initial jumping velocity decreased with increasing the difference in droplet sizes before coalescence. Actual jumping velocity was smaller than the theoretical value. When the sample was declined at 30 degrees, jumping frequency of water droplets repeated the increasing-decreasing cycle against cooling time and sustained droplet removal property. The jumping height of water droplets was remarkably increased under an external electric field.