具有微结构超疏水润湿梯度表面液滴的蒸发行为研究

Droplet Evaporation on the Wetting Gradient Super-hydrophobic Surface with Micro-structure

采用标准微电子机械系统(Micro-Electro-Mechanical System,MEMS)加工工艺,设计并加工了一种具有圆柱微结构的超疏水润湿梯度表面,搭建了研究液滴蒸发过程的可视化光学实验平台,同时从不同角度观察了液滴在具有圆柱状微结构超疏水润湿梯度表面的蒸发行为。通过实验研究发现:液滴在具有圆柱状微结构的超疏水润湿梯度表面的蒸发过程中,随着液滴的蒸发,液滴体积、液滴与表面的接触半径均不断减小,蒸发过程遵循混合蒸发模型;液滴边缘的三相线跳跃与移动均只发生在相对疏水的区域一侧;而在相对亲水的一侧,液滴边缘始终处于静止状态,直至液滴完全蒸发;在超疏水润湿梯度表面上的液滴蒸发过程中,液滴质心仅在具有润湿梯度的方向上移动,且液滴质心移动方向与润湿梯度方向相反(朝亲水侧移动)。最后基于液滴蒸发过程中的能量变化理论,解释了出现上述现象的原因。

A super-hydrophobic wetting gradient surface with cylindrical microstructure was designed and fabricated by standard Micro-Electro-Mechanical System(MEMS) process.A visual optical experimental platform for studying the droplet evaporation process was set up.The droplet evaporation behavior on the super-hydrophobic wetting gradient surface with cylindrical microstructure was observed from different directions.The results show that the droplet volume and contact radius are decreasing with the evaporation of droplets on the surface of super-hydrophobic wetting gradient with cylindrical microstructure.Evaporation process follows a mixed evaporation model.The three-phase line jump and movement of the edge occurs only on the side of the relatively hydrophobic region.On the relatively hydrophilic side,the edge of the droplet is pinning at the surface through the evaporation process.During droplet evaporation on the super-hydrophobic wetting gradient surface,the droplet barycenter moves only in the direction with the wetting gradient.And the droplet barycenter moves in the opposite direction to the wetting gradient(toward the hydrophilic side).Reasons for the above phenomenon are explained based on the energy change theory in the droplet evaporation process.