Micro-morphological Models for the Special Wettability of Locust and Moth Wing

Fang, Yan; Sun, Gang; Wang, Jing; Hou, Yongfang; Jin, Dandan; Bai, Luming

doi:10.2991/icmmcce-17.2017.69

Cited by 1 publication

(2 citation statements)

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“…This suggested small roll-off angles and weak water adhesion. Small roll-off angles are commonly found in opaque butterflies (15,28) and in Parantica sita and Parnassius glacialis, the two clearwing butterfly species studied to date (29).…”

Section: Resultsmentioning

confidence: 97%

“…Superhydrophobicity is thus a sine qua non condition for water repellency and self-cleaning. Opaque butterflies and moths typically have self-cleaning wings, as attested by small roll-off angles (15,28). Scarce relevant studies suggest that wing hydrophobicity may depend on wing microstructure (presence and type of scale in 26, scale type and insertion angle in 29), and on wing macrostructure: species with longer wings (4), or larger ratio of wing area to body mass (26) show higher hydrophobicity and wing shape was invoked to explain natural variations in hydrophobicity (4).…”

Section: Introductionmentioning

confidence: 99%

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Hydrophobicity in clearwing Lepidoptera: impact of scale micro and nanostructure, and trade-off with optical transparency

Gomez

Pairraire

Pinna

et al. 2021

Preprint

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In opaque butterflies and moths, scales ensure vital functions like camouflage, thermoregulation, and hydrophobicity. Wing transparency in some species - achieved via modified or absent scales - raises the question of whether hydrophobicity can be maintained and of it dependence on scale microstructural (scale presence, morphology, insertion angle, and coloration) and nanostructural (ridge spacing and width) features. To address these questions, we assessed hydrophobicity in 23 clearwing species differing in scale micro and nanofeatures by measuring static contact angle (CA) of water droplets in the opaque and transparent patches of the same individuals at different stages of evaporation. We related these measures to wing structures (macro, micro, and nano) and compared them to predictions from Cassie-Baxter and Wenzel models. We found that overall, transparency is costly for hydrophobicity and this cost depends on scale microstructural features: transparent patches are less hydrophobic and lose more hydrophobicity with water evaporation than opaque patches. This loss is attenuated for higher scale densities, coloured scales (for erect scales), and when combining two types of scales (piliform and lamellar). Nude membranes show lowest hydrophobicity. Best models are Cassie-Baxter models that include scale microstructures for erect scales, and scale micro and nanostructures for flat scales. All findings are consistent with the physics of hydrophobicity, especially on multiscale roughness. Finally, wing hydrophobicity negatively relates to optical transparency. Moreover, tropical species have more hydrophobic transparent patches but similarly hydrophobic opaque patches compared to temperate species. Overall, diverse microstructures are likely functional compromises between multiple requirements.

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Section: Resultsmentioning

confidence: 97%