Nees Institute for Biodiversity of Plants, University of Bonn, Meckenheimer Allee 170, Bonn, Germany.
Beilstein J Nanotechnol. 2011;2:228-36. doi: 10.3762/bjnano.2.27. Epub 2011 May 4.
Hierarchically structured flower leaves (petals) of many plants are superhydrophobic, but water droplets do not roll-off when the surfaces are tilted. On such surfaces water droplets are in the "Cassie impregnating wetting state", which is also known as the "petal effect". By analyzing the petal surfaces of different species, we discovered interesting new wetting characteristics of the surface of the flower of the wild pansy (Viola tricolor). This surface is superhydrophobic with a static contact angle of 169° and very low hysteresis, i.e., the petal effect does not exist and water droplets roll-off as from a lotus (Nelumbo nucifera) leaf. However, the surface of the wild pansy petal does not possess the wax crystals of the lotus leaf. Its petals exhibit high cone-shaped cells (average size 40 µm) with a high aspect ratio (2.1) and a very fine cuticular folding (width 260 nm) on top. The applied water droplets are in the Cassie-Baxter wetting state and roll-off at inclination angles below 5°. Fabricated hydrophobic polymer replicas of the wild pansy were prepared in an easy two-step moulding process and possess the same wetting characteristics as the original flowers. In this work we present a technical surface with a new superhydrophobic, low adhesive surface design, which combines the hierarchical structuring of petals with a wetting behavior similar to that of the lotus leaf.
许多植物的分层结构花（花瓣）具有超疏水性，但当表面倾斜时，水滴不会滚落。在这种表面上，水滴处于“Cassie 浸渍润湿状态”，也称为“花瓣效应”。通过分析不同物种的花瓣表面，我们发现了野生三色堇（Viola tricolor）花表面有趣的新润湿特性。该表面具有超疏水性，静态接触角为 169°，滞后性非常低，即不存在花瓣效应，水滴会像从荷叶（Nelumbo nucifera）上滚落一样。然而，野生三色堇花瓣表面没有荷叶的蜡晶。它的花瓣具有高锥形细胞（平均尺寸为 40 µm），高纵横比（2.1）和非常精细的角质折叠（宽度为 260nm）。施加的水滴处于 Cassie-Baxter 润湿状态，在低于 5°的倾斜角度下滚落。通过简单的两步模塑工艺制备了野生三色堇的疏水聚合物复制品，具有与原始花朵相同的润湿特性。在这项工作中，我们提出了一种具有新的超疏水性、低粘性表面设计的技术表面，它将花瓣的分层结构与类似荷叶的润湿行为结合在一起。
