Jiang Yinlong, Yang Zhou, Jiang Tingting, Shen Dongying, Duan Jieli
College of Engineering, South China Agricultural University, Guangzhou 510642, China.
Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou 510642, China.
Materials (Basel). 2022 Jan 25;15(3):917. doi: 10.3390/ma15030917.
Janus wettability plays an important role in certain special occasions. In this study, field emission scanning electron microscopy (FESEM) was used to observe the surface microstructure of banana leaves, the static wettability of the banana leaf surface was tested, and the dynamic response of water droplets falling at different heights and hitting on the adaxial and abaxial sides was studied. The study found that the nanopillars on the adaxial and abaxial sides of the banana leaf were different in shape. The nanopillars on the adaxial side were cone-shaped with large gaps, showing hydrophilicity (Wenzel state), and the heads of the nanopillars on the abaxial side were smooth and spherical with small gaps, showing weak hydrophobicity (Cassie-Baxter state). Banana leaves show Janus wettability, and the banana leaf surface has high adhesion properties. During the dynamic impact test, the adaxial and abaxial sides of the banana leaves showed different dynamic responses, and the wettability of the adaxial side of the banana leaves was always stronger than the abaxial side. Based on the structural parameters of nanopillars on the surface of the banana leaf and the classical wetting theory model, an ideal geometric model around a single nanopillar on both sides of the banana leaf was established. The results show that the established model has high accuracy and can reflect the experimental results effectively. When the apparent contact angle was 76.17°, and the intrinsic contact angle was 81.17° on the adaxial side of the banana leaf, steady hydrophilicity was shown. The abaxial side was similar. The underlying mechanism of Janus wettability on the banana leaf surface was elucidated. This study provides an important reference for the preparation of Janus wettability bionic surfaces and the efficient and high-quality management of banana orchards.
双面润湿性在某些特殊场合中起着重要作用。在本研究中，使用场发射扫描电子显微镜（FESEM）观察香蕉叶的表面微观结构，测试香蕉叶表面的静态润湿性，并研究不同高度下落的水滴撞击香蕉叶正面和背面时的动态响应。研究发现，香蕉叶正面和背面的纳米柱形状不同。正面的纳米柱呈锥形，间隙较大，表现出亲水性（文泽尔状态），而背面的纳米柱头部光滑呈球形，间隙较小，表现出弱疏水性（卡西 - 巴克斯特状态）。香蕉叶表现出双面润湿性，且香蕉叶表面具有高粘附性能。在动态冲击测试中，香蕉叶的正面和背面表现出不同的动态响应，香蕉叶正面的润湿性始终强于背面。基于香蕉叶表面纳米柱的结构参数和经典润湿理论模型，建立了香蕉叶两侧单个纳米柱周围的理想几何模型。结果表明，所建立的模型具有较高的准确性，能够有效反映实验结果。当香蕉叶正面的表观接触角为76.17°，本征接触角为81.17°时，表现出稳定的亲水性。背面情况类似。阐明了香蕉叶表面双面润湿性的潜在机制。本研究为制备双面润湿性仿生表面以及香蕉园的高效优质管理提供了重要参考。
