猪笼草滑移区微纳复合结构液滴浸润程度的数值模拟

Numerical Simulation of Droplet Infiltration of Micro-nano Structure in Nepenthes Slippery Zone

猪笼草滑移区因具有微纳复合结构而呈现超疏水润湿特性,为超疏水表面研制提供了潜在的仿生原型,但其超疏水润湿机理仍未得到充分揭示,这源于现有技术手段不能准确获取液滴对滑移区微纳复合结构的浸润程度。构建滑移区微纳复合结构(月骨体、蜡质晶体)的三维模型,划分网格并对液滴网格单元的顶点进行受力分析;然后基于最小能量原理并采用Surface Evolver软件进行液滴对滑移区微纳复合结构浸润过程的数值模拟,获取不同浸润程度下的液滴形貌特征;基于Young-Lapalace拟合法得到液滴在滑移区表面的理论接触角,当液滴对微纳复合结构的浸润率为0.7~0.8时其值为155.0°~155.4°。为检验所构建模型的有效性,利用光学接触角测量仪测试了超纯水液滴在滑移区表面的接触角(155.1°±1.3°,n=20),这与数值模拟获取的理论接触角高度吻合,据此确定液滴对滑移区微纳复合结构的浸润率介于0.7~0.8。研究结果为液滴对超疏水微纳复合结构浸润程度的定量表征提供了可借鉴的方法,为猪笼草滑移区超疏水润湿机理的充分揭示提供理论支持,并能够促其成为仿生原型用于机械工程领域的超疏水表面研制。

The Nepenthes slippery zone depends on its micro-nano structure to appear superhydrophobic wettability,which provides a biomimetic prototype for the development of superhydrophobic surface.However,the mechanism of superhydrophobic wettability has not been fully revealed,because the infiltration degree of liquid droplets to micro-nano structure of Nepenthes slippery zone has not been accurately acquired via the existing technology.The structure model of Nepenthes slippery zone(lunate cell,waxy crystal)is constructed,the structure model is meshed and the force analysis of ultrapure-water droplet is carried out.Based on the minimal energy principle,the infiltration process of ultrapure-water droplet to the Nepenthes slippery zone is numerically simulated with the Surface Evolver software,and the morphology of ultrapure-water droplet under different infiltration degree was obtained.According to the Young-Lapalace equation fitting method,theoretical contact angle of ultrapure-water droplets on the Nepenthes slippery zone was obtained,which has the values of 155.0°~155.4°under the infiltration ratio of 0.7~0.8.To verify the validity of the numerical simulation model,the contact angle of ultrapure-water droplet is measured with the optical contact angle measuring system,showing the value of 155.1°±1.3°,n=20.This contact angle is highly consistent with the theoretical contact angle obtained from the numerical simulation,indicating the infiltration ratio of ultrapure-water droplet to the Nepenthes slippery zone is 0.7~0.8.Our obtained results provide a potential method for quantitative characterization of infiltration degree produced by liquid droplet to micro-nano structure of superhydrophobic surface,and supply theoretical foundation for fully revealing the superhydrophobic mechanism of Nepenthes slippery zone,which can promote the Nepenthes slippery zone to become a biomimetic prototype used to design superhydrophobic materials.