猪笼草叶笼滑移区各向异性超疏水润湿特性表征与机理分析

为获取各向异性超疏水表面研制的仿生原型,采用接触角测量仪测试表征了猪笼草(Nepenthes alata)叶笼滑移区的各向异性超疏水润湿特性,采用扫描电镜和三维形貌干涉仪观测滑移区形貌结构并提取三维特征信息,分析滑移区形貌结构对各向异性超疏水润湿特性的影响机理。结果表明:水滴在滑移区的接触角为(155.07±1.14)°,朝向叶笼底部和顶部的滚动角分别为(2.82±0.45)°和(5.40±0.31)°;滑移区覆盖着两端朝向叶笼内部弯曲且具有不对称凸面表层轮廓的微米级月骨体,以及形貌轮廓不规则且交错排列成致密孔洞结构的纳米级蜡质晶体,其中能够蓄留空气的蜡质晶体是产生超疏水润湿特性的重要因素;月骨体在不同方向的斜坡结构、悬崖结构致使水滴在滑移区滚动难易程度呈现差异,从而导致滚动角的显著不同与各向异性超疏水润湿现象的产生。

Anisotropic superhydrophobic wettability measurement and mechanism analysis of slippery zone in Nepenthes pitchers

To find the bionic prototypes used to designing superhydrophobic surfaces with anisotropic properties, the anisotropic superhydrophobic wettability of slippery zone in Nepenthes pitcher was measured via a contact angle meter. The morphology/structure of the slippery zone was examined via a scanning electron microscope and a scanning white-light interferometer to obtain their structure parameters, and the influence mechanism of structure characteristics on anisotropic superhydrophobic wettability was analyzed. The results show that: The contact angle of water droplet on the slippery zone is(155. 07±1. 14)°, and the sliding angle of the slippery zone toward pitcher in bottom and up are(2. 88±0. 45)° and(5. 40±0. 31)°, respectively. The slippery zone is covered by a large number of lunate cells with micron-scaled structure parameters, and their both ends bend toward pitcher bottom to form a crescent-shaped profile with an asymmetrical convex surface. Plenty wax coverings are densely and continuously distributed on the slippery zone. It appears as discernible platelet-formed wax crystals with an irregular pattern and nano-scaled structure parameters overlapping with each other to form plenty of distinguishable cavities. The wax coverings depend on their cavities to trap air and become an important factor to make the slippery zone present superhydrophobic wettability. Lunate cell''s slope and precipice structure make the rolling of water drops displaying different degrees of difficulty at slippery zone, resulting in the anisotropic superhydrophobic wettability of slippery zone.