Abstract
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.
Highlights
Introduction published maps and institutional affilWith the evolution of biology, a specific structure has been formed on the surface of animals and plants to adapt to the living environment, which has become one of the hotspots of biologically efficient production management and bionics research
The water contact angles (CAs) and rolling angles (RAs) of the banana leaf surface were measured at three different positions (Tip, Middle, and Base) on the adaxial and abaxial sides
The test results of the contact angles of 6 μL water droplets on the banana leaf surface showed that the contact angle on the adaxial side was 76.08◦ ± 2.01◦, showing hydrophilicity, and the contact angle on the abaxial side was 94.32◦ ± 1.04◦, showing weak hydrophobicity
Summary
With the evolution of biology, a specific structure has been formed on the surface of animals and plants to adapt to the living environment, which has become one of the hotspots of biologically efficient production management and bionics research. The “Van der Waals force” generated between the large number of fine hairs on the soles of the gecko’s feet and the molecules on the surface of the object is accumulated to form a high adhesion force, which enables it to travel freely on the wall [2]. The researchers conducted research on a large number of animal iations.
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