How Micro/Nanoarchitecture Facilitates Anti-Wetting: An Elegant Hierarchical Design on the Termite Wing

TLDR

Termite wings are large relative to body mass, weak flyers that often take off during rain, yet water droplets spontaneously roll off their surfaces. The study demonstrates that the termite wing’s hierarchical array design achieves anti‑wetting by reducing contact area and adhesion across droplets of various sizes. The anti‑wetting mechanism relies on a nano‑architectured hair array coated with a hydrophobic polymer and an underlying non‑wetting membrane of star‑shaped microstructures that together minimize droplet contact. The micro/nano‑structured hierarchy yields scale‑independent non‑wetting while minimizing weight and material, offering insights into insect wing evolution.

Abstract

The termite is an insect which is a weak flier, has a large wing area in relation to its body mass, and many species typically fly during rain or storm periods. Water droplets placed on these insects' wings will spontaneously roll off the surface. Here we show how the intricate hierarchical array design of these insect wings achieves anti-wetting properties with water bodies of various sizes by reducing contact area and thus adhesion. To repel large droplets, the termite uses an array of hairs with a specially designed nanoarchitecture, which we demonstrate is critical for this function. By coating single hairs with a polymer of varying thicknesses (with a similar hydrophobicity to insect cuticle), we demonstrate that hairs of the same chemistry and with the complete nanoarchitecture show the greatest resistance to penetrating water bodies. The wings also consist of an underlying non-wetting membrane substructure comprising an array of star-shaped microstructures which minimize interaction with micro-sized droplets of water. The sophisticated micro/nanostructured hierarchy on the termite wing membrane not only results in non-wetting at different length scales but also demonstrates a design for weight and material minimization while achieving this state. Elucidating the function of such structures has implications for understanding insect biology and the evolution of wings.