Static shape of liquid droplets on textured surface draws significant attention from the standpoint of several engineering applications, ranging from heat transfer to bio-printing. This paper discusses the equilibrium behavior of a nanoliter size droplet dispensed on a micropatterned surface. For a given combination of intrinsic wettability of the surface, liquid surface tension and the geometric morphology of the textured surface, the liquid droplet prefers to be on Cassie-Baxter, Wenzel or an intermediate, hybrid state. Here we have carried out an energy-based simulation of nanoliter size droplets on micropatterned surface, using an open-source surface evolver fluid interface tool SE-FIT. A simplified periodic geometry of rectangular (straight or tapered) micro-pillars of specified dimensions is chosen for the micropatterned surface. For a given solid surface texture, we found that droplet prefers to transit from Wenzel to Cassie state beyond a threshold intrinsic sessile contact angle (which the liquid would have subtended on a microscopically smooth surface of the same solid material). This critical transition contact angle is plotted against the roughness parameter. Present study helps in designing the wettability-engineered surfaces for specific engineering applications.

从传热到生物打印等多种工程应用的观点，带纹理表面上液滴的静态形状引起了极大的关注。本文讨论了微图案表面上分配的纳升大小的液滴的平衡行为。对于表面的固有润湿性，液体表面张力和纹理化表面的几何形态的给定组合，液滴更倾向于处于Cassie-Baxter，Wenzel或中间的混合状态。在这里，我们使用开源表面演化器流体接口工具SE-FIT对微图案化表面上的纳升大小的液滴进行了基于能量的模拟。选择具有指定尺寸的矩形（直形或锥形）微柱的简化周期性几何图形作为微图案化表面。对于给定的固体表面纹理，我们发现液滴更喜欢从Wenzel过渡到Cassie状态，超过阈值固有固着接触角（该固相接触角液体将浸入在相同固体材料的微观光滑表面上）。将该临界过渡接触角与粗糙度参数作图。本研究有助于设计用于特定工程应用的可润湿性工程表面。