Wettability of a droplet on rough solid surface exhibits complex behavior compared with a droplet on smooth solid surface. On a hydrophilic / hydrophobic solid substrate, hydrophilicity / hydrophobicity of a droplet changes as the surface roughness of the solid substrate varies. This kind of wettability is mainly discussed on the basis of Wenzel and Cassi-Baxter models where the wettability of droplets on roughened surface is analyzed by the concept of roughness ratio and contact area fraction. However, in an actual situation, it is very difficult to quantify the structure of the roughened surface and the contact area between liquid and solid surface strictly. In the present study, wettability of water-ethanol binary mixture droplet on roughened low-surface-energy solid is experimentally investigated in order to understand the wetting behavior in wide range of surface tension of liquid. A simple morphological model to quantify the surface roughness and critical surface tension of roughened solid surface is proposed. In addition, analytical model to predict the wettability on roughened solid surface is developed on the basis of the concept of adsorption of liquid molecules at solid–liquid interface, which can be applied to wetting behavior on both hydrophilic and hydrophobic roughened solid substrates.

与光滑固体表面上的液滴相比，粗糙固体表面上的液滴的润湿性表现出复杂的行为。在亲水性/疏水性固体基质上，液滴的亲水性/疏水性随着固体基质的表面粗糙度的变化而变化。这种润湿性主要在Wenzel和Cassi-Baxter模型的基础上进行讨论，其中通过粗糙度比和接触面积分数的概念分析了液滴在粗糙表面上的润湿性。然而，在实际情况中，很难严格地量化粗糙表面的结构和液体与固体表面之间的接触面积。在目前的研究中，通过实验研究了水-乙醇二元混合物液滴在粗糙的低表面能固体上的润湿性，以了解在较大的液体表面张力范围内的润湿行为。提出了一种简单的形态学模型来量化粗糙化固体表面的表面粗糙度和临界表面张力。另外，在固液界面吸附液体分子的概念的基础上，建立了预测粗糙表面固体润湿性的分析模型，该模型可应用于亲水性和疏水性粗糙固体基质的润湿行为。