亲水性微观粗糙表面润湿状态转变性能研究

以亲水性微观粗糙表面上不同几何形貌及分布的微柱阵列为对象, 讨论了液滴在亲水性粗糙表面上的润湿过程以及润湿状态的转变阶段. 从能量角度分别考察了微观粗糙结构几何形貌及分布、微柱几何参数、固体表面亲水性、接触角滞后作用等因素对液滴润湿状态转变的影响规律. 研究发现: 在亲水粗糙表面, 正方形微柱呈正六边形阵列分布时, 液滴更容易形成稳定的Cassie状态, 或者液滴仅发生Cassie状态向中间浸润状态的转变; 与此同时, 减小微柱间距、增大方柱宽度或圆柱直径、增大微柱高度、增强固体表面的亲水性将有利于液滴处于稳定的Cassie状态, 或阻止润湿状态向伪-Wenzel或Wenzel状态转变; 然而, 当液滴处于Cassie状态时, 较小的固-液界面面积分数或减弱固体表面亲水性能均有利于增大液滴的表观接触角, 因此在亲水表面设计粗糙结构时应综合考虑润湿状态稳定性和较大表观接触角两方面因素; 此外, 接触角滞后作用对于液滴状态的稳定性以及疏水性能的实现具有相反作用的影响. 研究结果为液滴在亲水表面获得稳定Cassie状态的粗糙结构设计方法提供了理论依据. 关键词： 亲水表面 微观粗糙结构 表面自由能 润湿状态转变

Wetting state transition on hydrophilic microscale rough surface

The wetting process and the wetting state transition stages are studied on hydrophilic rough surfaces covered with microscale pillar arrays of different geometrical morphologies and distributions. The effects of geometrical morphology, distribution, parameters, hydrophilicity, and contact angle hysteresis of pillar arrays on wetting state transition are analyzed by an energy method. The results indicate that on the hydrophilic rough surface covered with hexagonal arrays of square pillars, the water droplet tends to stay in a stable Cassie state, or the wetting state transits only from a Cassie state to an intermediate state. Moreover, smaller pillar interval, larger square pillar width or diameter of cylinder, higher pillar height, strong hydrophilicity are beneficial to the stability of Cassie state, therefore, the wetting state could be prevented from transforming to pseudo-Wenzel state or Wenzel state. However, smaller area fraction of solid-liquid interface under the water drop and weaker hydrophilicity is beneficial to increasing the apparent contact angle. Therefore, the stability of wetting state and the large apparent contact angle should be considered in hydrophilic surface design. The contact angle hysteresis gives rise to an opposite effect on wetting state stability and the hydrophobicity or superhydrophobicity of rough solid surface. The results provide a theoretical foundation for designing the substrates covered with hydrophilic rough structures, on which the water droplet will obtain a stable Cassie state.
Keywords： hydrophilic surface microscale rough structure surface energy wetting state transition