超疏水表面液滴合并诱导弹跳现象分析

在紫铜基表面上制备了具有微纳结构的十八烷基硫醇自组装超疏水表面，采用高速摄像和显微技术研究了水平表面上液滴合并运动特性。实验结果表明，超疏水表面上液滴合并过程中释放出的表面能可以克服表面黏附作用诱发液滴弹跳现象，液滴越小，弹跳高度越大。考虑液滴表面黏附功、液滴运动引起的黏性耗散能等，根据能量守恒原理进行了理论分析。理论分析结果表明，液滴合并诱导弹跳现象存在最小液滴半径约为39.9 μm；随着液滴半径的增大，液滴弹跳高度增大，液滴半径为83.7 μm时达到弹跳最大高度点，随着液滴半径继续增大，液滴弹跳高度减小，直至最大半径约3.9 mm时，无液滴弹跳现象发生而是在合并位置发生脉动。

Characteristics of droplet coalescence and self-propelling on superhydrophobic surface

Superhydrophobic surface was prepared by self-assembled monolayers coatings of n-octadecyl mercaptan on the nanostructured copper substrate.Characteristics of movement dynamics feathers induced by droplet coalescence were investigated by high speed camera and microsurgical technique on horizontal superhydrophobic surface.Experimental results indicate that droplet jumping phenomenon induced by the energy difference between surface energy released by droplet coalescence and surface adhesion effect can be obtained.The smaller the initial droplet is,the higher the coalescent droplet jumps.Theoretical analysis is presented based on the energy conservation.Surface adhesion energy and viscous dissipation caused by droplet movement are also considered.Theoretical results show that droplet jumping phenomenon induced by droplet coalescence can occur when droplet radius is larger than the minimum droplet radius.The minimum droplet radius is approximate 39.9 μm.Droplet jumping height increases with an increase of droplet radius.However,droplet jumping height will decrease with an increase of droplet radius when droplet radius is larger than the critical value.The maximum jumping height can be obtained when droplet radius equals to 83.7 μm.Droplet jumping phenomenon will disappear when droplet radius is larger than 3.9 mm.However,droplet pulsation phenomenon on droplet coalescence position can be found in the meanwhile.