Wettability and Contaminability of Insect Wings as a Function of Their Surface Sculptures

Abstract

Wagner, T., Neinhuis, C. & Barthlott, W. 1996. Wettability and contaminability of insect wings as a function of their surface sculptures. Acta Zoologica (Stockholm) 76: 213-225.The wing surfaces of 97 insect species from virtually all relevant major groups were examined by high resolution scanning-electron-microscopy, in order to identify the relationships between the wing microstructures, their wettability with water and their behaviour under the influence of contamination.Isolated wings with contact angles between 31.6" and 155.5" were artificially contaminated with silicate dusts and subsequently fogged until drops of water ("dew") formed and rolled off. The remaining particles were counted via a digital image analysis system. Remaining particle values between 0.41% and 103% were determined in comparison with unfogged controls. Some insects with very unwettable wings show a highly significant "self-cleaning" effect under the influence of rain or dew.Detailed analysis revealed that there is a correlation between the wettability and the "SM Index" (quotient of wing surface/(body mass)06') with values ranging from 2.42 to 57.0. Furthermore, there is a correlation between the "self-cleaning" effect and the SM Index, meaning that taxa with a high SM Index, e.g. "large-winged Ephemeroptera, Odonata. Planipennia, and many Lepidoptera. have very unwettable wings and show high particle removal due to dripping water drops. The "smallwinged" insects, such as Diptera and Hymenoptera, and insects with elytra, such as Blattariae, Saltatoria, Heteroptera and Coleoptera, show completely opposite effects. This is clearly a result of the fact that species with a high SM Index are, in principle, more restricted in flight by contamination than species with a low SM Index which can also actively clean their own wings. The wings primarily serve a protection function in insects with elytra, so that the effects of contamination are probably of minor importance in these insects.

Bat wing sensors support flight control

“…In insects a dense grid of very short hair-like structures on the wing are thought to primarily make the wing water repellent (18). Flight control is achieved by different structures, some of which are located at the wing base or on the wing margin, others are located elsewhere on the insect's body.…”

Fouling of nanostructured insect cuticle: adhesion of natural and artificial contaminants

“…Macrotrichia have been found to add a secondary layer of protection against surfaces with which the insect may come into contact (Watson et al 2010b). The lacewing surface of the species Chrysoperla carnea has been previously studied where the wing was exposed to a fine dust of silica particles under fogging conditions and was shown to exhibit a high degree of non-contaminability (Wagner et al 1996).…”

“…Additional weight due to contamination (water and/or contaminating particles) can potentially have a detrimental effect on the insects' flight capabilities (Wagner et al 1996). Wagner et al (1996) demonstrated a correlation between contaminability, wettability and the wing area of many insects. They exposed insect specimens to a fine silica dust and fogging conditions.…”

Physics and applications of superhydrophobic and superhydrophilic surfaces and coatings

“…79 The now commonly accepted meaning of a superhydrophobic surface is a surface on which the water (advancing) contact angle is at least 150°, and the contact angle hysteresis as well as the sliding (or rolling off) angle (sliding/rolling angle is the minimum angle of sloped solid at which water (liquid) drop rolls off the surface) do not exceed 5-10° (Table 2). Although currently superhydrophobic surfaces are inspired by biological specimens, [80][81][82][83][84][85][86][87][88][89][90][91][92][93][94][95][96][97] the early research was inspired by the practical need to enhance coating repellency of water and snow. 98,99 These days, superhydrophobic coatings are manufactured by chemical, physical and/or mechanical modifications of both organic and inorganic materials.…”