Wettability of dragonfly wings: the structure detection and theoretical modeling

Abstract

Hydrophobic surfaces have gained extensive attention in recent decades for their potential applications. The hydrophobic properties of dragonfly's (Pantala flavescens) wings were measured, and the water contact angles (WCAs) of the distal and basal part of a dragonfly's wing were 134.9 and 125.8 , respectively. Images obtained by optical microscopy and scanning electron microscopy showed the microstructures and nanostructures on the wing surface. Microstructures appeared as cell block patterns, and the size of the blocks decreased from the basal to distal part. However, no significant differences of chemical composition between the two parts were detected by X-ray photoelectron spectroscopy. To understand the correlation between the structures and WCA, a double roughness structure model was built theoretically with simplified lattice patterns, and the theoretical model was well fitted with empirical wettability of the dragonfly's wing.

Wing wettability gradient in a damselflyLestes sponsa(Odonata: Lestidae) reflects the submergence behaviour during underwater oviposition

“…In accordance with our assumptions, we found significant spatial differences in the wettability of the L. sponsa wings. Contrary to the previously published studies on the wettability of different wing regions in both dragonflies and damselflies [ 35 , 39 ], we found the tip to be the least hydrophobic of all measured wing parts, and the hydrophobicity gradually increased towards the most proximal part. Unlike in some of the studies reporting CA values for the odonate wings [ 1 , 7 , 29 , 30 , 36 ], in L. sponsa , the wing surface as a whole was not superhydrophobic, as the mean values of advancing CA, receding CA and CAH for all measured regions were 129.3°, 97.1° and 32.1°, respectively, which was well below the superhydrophobicity threshold values (i.e.…”

“…Odonate wings have been found to possess spatially heterogeneous wettability characteristics, with the surface micro- and nanostructure and topography playing a key role in determining these heterogeneities [ 29 , 34 , 35 , 39 ]. There is a number of studies focusing on the wettability of odonate wings in the context of application to industry or medicine, as they are valuable for the reconstruction of wing structures as a biomimetic template [ 1 , 7 , 16 , 29 , 30 , 34 , 35 , 39 – 41 ]. However, in ecological and/or evolutionary context, such studies are very rare, for example, the one dealing with sex- and age-related differences in hydrophobic structures of a damselfly Calopteryx splendens [ 36 ], or one examining submergence potential of C. cornelia [ 33 ].…”

Mechanisms of hydrophobization of polymeric composites etched in CF4plasma

“…During the experiments, the water drop was firmly sticking to the composite surface, which restricted the easy rolling of the drop from the surface. Such sticky nature arises because of the pinning of water drop inside the micro textures on the surface, which can be described by Wenzel state mechanism . The fact that water droplet stuck to the surface even after changing the tilting angle to 90° even further supported this argument.…”

Complete neuroanatomy of dragonfly wings suggests direct sensing of aeroelastic deformations

“…Dragonfly wings are extensively innervated by sensory neurons, but what external cuticular structures are these neurons innervating? Odonate wing membranes are smooth, but their veins are covered in an array of microscopic structures with a variety of roles (Rajabi et al, 2011;Gao et al, 2013). Some microstructures resemble sensors, but are not innervated.…”