凸起微结构对超疏水表面液滴弹跳强化机理的研究

摘要

Studies show that coalescence-induced droplet jumping on superhydrophobic surfaces (SHSs) can be enhanced by regulating the impact position of a liquid bridge on the substrate. Flat SHSs with only nanostructures and SHSs with raised structures (triangular prisms) were fabricated in this study. The dynamic behaviors of droplet jumping on flat SHSs were captured from both side and bottom view with a high-speed camera. Droplet jumping velocities were measured and the corresponding energy conversion efficiencies were calculated to investigate the effect of triangular prism on droplet jumping. The results show that the coalescence-induced droplet jumping process can be divided into four stages: (I) expansion of the liquid bridge between two droplets; (II) impact of the liquid bridge on the surface; (III) retraction of the droplet base area; (IV) deceleration of the coalesced droplet in the air. For droplet coalescence upon the superhydrophobic triangular prism, the droplet jumping velocities increase with the length of the triangular prism, while the height is kept constant until a maximum value is reached. The droplet jumping velocities also increase with the height of the triangular prism when the length is kept constant.%研究表明冷凝液滴在超疏水表面上合并时可以诱发弹跳,而调控液桥撞击壁面的位置能够强化这一过程.今制备了两种构型的超疏水表面(只包涵纳米结构的平壁超疏水表面以及带有三棱柱凸起结构的超疏水表面),从液滴侧部和底部两个方向协同拍摄了液滴在平壁超疏水表面上合并弹跳动态过程;实验测量了液滴弹离壁面的速度并计算了相应的能量转化率,研究了三棱柱的结构参数对液滴弹跳速度的影响.结果表明,超疏水表面上液滴合并诱导弹跳过程可以分为四个阶段:液桥生长、液桥撞击壁面、液滴底面积收缩及液滴弹离壁面;当液滴在三棱柱凸起结构上方合并时,液滴弹离壁面的速度随着三棱柱长度增加而增大(三棱柱高度不变),且存在一个最大值;当三棱柱长度一定时,液滴弹离壁面的速度亦随着三棱柱的高度增加而增大.