Abstract The hydrophobic stability to prevent Cassie-Wenzel (C-W) transition is an important property of superhydrophobic surfaces, which is mainly controlled by the micro/nano structure of surfaces. Based on the contact lines (CLs) around and inside the contact region, we analyzed the applied forces on a static sessile droplet deposited on the hydrophobic micropillar-structured surface. A simplified double-radius fitting method was derived to outline the contour of the droplet, and a force-balance model was gained to describe the critical conditions of the C-W transition. Compared with the classical force-balance models, the theoretical predictions from the proposed model agree much better with the experimental results. A reliable estimation of the critical conditions for the C-W transition during evaporation can be readily formed by integrating the depinning mechanism of the receding CL on the micro-patterned surfaces into our model, which obviously cannot be obtained by the classical force-balance models. The effects of gravity and surface tension in the proposed equilibrium model for the C-W transition reach a compromise. The introduction of surface tension acting on the apparent CL in our model will help to provide appropriate geometric parameters for microstructures on the superhydrophobic surfaces to achieve high hydrophobic stability.

中文翻译：

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疏水微柱结构表面上固着液滴的 Cassie-Wenzel 转变的基于接触线的模型

摘要 防止Cassie-Wenzel (CW)转变的疏水稳定性是超疏水表面的一个重要特性，主要受表面微/纳米结构的控制。基于接触区域周围和内部的接触线 (CL)，我们分析了施加在沉积在疏水微柱结构表面上的静态固着液滴上的力。导出了一种简化的双半径拟合方法来勾勒液滴的轮廓，并获得一个力平衡模型来描述 CW 转变的临界条件。与经典的力平衡模型相比，所提出模型的理论预测与实验结果更加吻合。通过将微图案表面上后退 CL 的脱钉机制整合到我们的模型中，可以很容易地形成对蒸发过程中 CW 转变临界条件的可靠估计，这显然无法通过经典的力平衡模型获得。重力和表面张力在提出的 CW 过渡平衡模型中的影响达到了折衷。在我们的模型中引入作用于表观 CL 的表面张力将有助于为超疏水表面上的微结构提供适当的几何参数，以实现高疏水稳定性。重力和表面张力在提出的 CW 过渡平衡模型中的影响达到了折衷。在我们的模型中引入作用于表观 CL 的表面张力将有助于为超疏水表面上的微结构提供适当的几何参数，以实现高疏水稳定性。重力和表面张力在提出的 CW 过渡平衡模型中的影响达到了折衷。在我们的模型中引入作用于表观 CL 的表面张力将有助于为超疏水表面上的微结构提供适当的几何参数，以实现高疏水稳定性。