Abstract: The dynamic behavior of droplets impacting on micropillared and micropored surfaces was investigated in this paper. The results showed that when the droplet impacted on the micropillared surface,the droplet appeared the spreading and retraction processes. With the increase of Weber number(We),the spreading diameter increased. Meanwhile,the satellite droplets appeared. However,the time to reach the maximum spreading diameter was the same. When the droplet with the same velocity(the same We) impacted on micropillared surfaces with different pitch between micro pillars,the maximum spreading diameter decreased with the increase of the pitch,and the wetting state was instability. The wetting state transited from the Cassie state to the Wenzel state during the spreading process. When the pitch was small,The smaller the adhesion work is,the more likely to occur to the Cassie state. Moreover,the dynamic behaviors of a droplet impacting on micropored hydrophobic surfaces were compared with the micropillared surfaces. The droplet was spreading and retracting on micropored surfaces. In the impacting process,the wetting state did not transit into the Wenzel state. The phenomenon was analyzed by using the established physical model.

Key words: droplets, impact, surface, microstructure, instability

摘要： 对去离子水滴撞击不同几何尺寸显微结构方柱和方孔状疏水表面的动态特性进行了研究。结果表明：当液滴以不同速度撞击微方柱疏水表面时，液滴展现铺展和回缩过程，且随着韦伯数（We数）增大，最大铺展直径增大，并伴随卫星液滴出现，但到达最大铺展直径的时间一致；而当液滴以相同的速度（We数相同）撞击间距不同的微方柱疏水表面时，液滴的最大铺展直径随着间距的增大而减小，且铺展过程会液滴浸润状态变得不稳定，发生由Cassie向Wenzel状态的浸润转变。当微方柱间距较小时，液滴受到的黏附功越小，越易发生向Cassie状态的转变；液滴撞击微方孔疏水表面时，液滴以规则的圆环状向外铺展和回缩，最后呈现近似规则的椭球状，不会发生向Wenzel状态的浸润转变，利用建立的物理模型对前述现象进行了分析。

关键词: 水滴, 撞击, 表面, 显微结构, 不稳定性