Liquid fresh water is scarce in arid and semi-arid regions. Some organisms in these stressful habitats are well adapted to the environmental conditions and obtain fresh water directly from the atmosphere. This ability of “moisture harvesting” relies on specific microstructural features organisms exhibit at their external surfaces. In this respect, the dew harvesting ability of the arid plant species Opuntia stricta (Cactaceae) has been investigated. Its tiny stem spines, known as glochids, have a unique microstructure, ordered in hierarchical manner with an anisotropic surface. The glochids are covered with cone-shaped barbs and have dense mats of hygroscopic trichomes at the base. Dew harvesting ability in O. stricta seems to be controlled by three driving forces, namely: Laplace pressure difference, Wenzel relation and differences in wettability. The formation of special external microstructural features supporting this ability represents an adaptive trait in O. stricta to dry arid environments. Studying such structures in detail will give insights on how biomimetic inspired devices may contribute to optimize moisture harvesting in dry regions.

在干旱和半干旱地区稀缺的液态淡水。这些压力大的栖息地中的某些生物非常适应环境条件，并直接从大气中获取淡水。这种“水分收集”的能力取决于生物体在其外表面表现出的特定的微观结构特征。在这方面，已经研究了干旱植物仙人掌仙人掌（Cactaceae）的结露能力。它的微小茎棘，被称为毛线虫，具有独特的微观结构，以各向异性的表面分层排列。针刺被圆锥形的倒钩覆盖，并在基部具有吸湿毛状体的致密垫。在露捕获能力O. STRICTA似乎是由三个驱动力控制的，即：拉普拉斯压差，Wenzel关系和润湿性差异。支持这种能力的特殊外部微结构特征的形成代表了O. stricta对干旱干旱环境的适应性特征。详细研究此类结构将提供有关仿生启发式设备如何有助于优化干旱地区水分收集的见解。