Abstract
Inner surface of Nepenthes slippery zone shows anisotropic superhydrophobic wettability. Here, we investigate what factors cause the anisotropy via sliding angle measurement, morphology/structure observation and model analysis. Static contact angle of ultrapure-water droplet exhibits the value of 154.80°–156.83°, and sliding angle towards pitcher bottom and up is 2.82 ± 0.45° and 5.22 ± 0.28°, respectively. The slippery zone under investigation is covered by plenty of lunate cells with both ends bending downward, and a dense layer of wax coverings without directional difference in morphology/structure. Results indicate that the slippery zone has a considerable anisotropy in superhydrophobic wettability that is most likely caused by the lunate cells. A model was proposed to quantitatively analyse how the structure characteristics of lunate cells affect the anisotropic superhydrophobicity, and found that the slope/precipice structure of lunate cells forms a ratchet effect to cause ultrapure-water droplet to roll towards pitcher bottom/up in different order of difficulty. Our investigation firstly reveals the mechanism of anisotropic superhydrophobic wettability of Nepenthes slippery zone, and inspires the bionic design of superhydrophobic surfaces with anisotropic properties.
Highlights
Nepenthes (Nepenthaceae) plants of the carnivorous specie have evolved a specialized organ, namely pitcher that grows from the royalsocietypublishing.org/journal/rsos R
Our obtained results concerning the wettability and structure characteristics indicate that the Nepenthes slippery zone has the anisotropic superhydrophobicity, and the ratchet effect produced by lunate cells is the exclusive causation
Anisotropic wettability of the Nepenthes slippery zone was comprehensively characterized via sliding angle measurement, morphology/structure observation
Summary
Nepenthes (Nepenthaceae) plants of the carnivorous specie have evolved a specialized organ, namely pitcher that grows from the royalsocietypublishing.org/journal/rsos R. Most insects find the highly evolved slippery zone has considerably unique slippage properties, that execute the function of retaining prey [11]. In recent years, both the morphology/structure and the predation function of the slippery zone have gradually attracted a large number of investigations, attempting to establish bionic prototypes for developing insect slippery trapping plates [10,12,13,14,15] and other bioinspired materials with anti-adhesive properties [16,17,18,19,20,21]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
