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Title:Micro- and nanoscale features of insect cuticle and their impacts on wetting, friction, and optical properties
Author(s):Reiter, Kristen E.
Advisor(s):Alleyne, Marianne
Contributor(s):Suarez, Andrew; McElrath, Thomas; Dunn, Alison
Department / Program:Entomology
Degree Granting Institution:University of Illinois at Urbana-Champaign
diffraction grating
Abstract:The surface of insect cuticle is often modified to form various unique structures such as setae, microtrichia, nanopillars, sculpticells, or gratings. The adaptive roles of these cuticular architectures have become a recent area of interest, notably to serve as inspiration for the creation of novel materials because they result in desirable functionalities such as anti-wetting, anti-reflective, and self-cleaning properties. The unique structures found on fly wings and beetle elytra and tergites and their effects on physical properties are investigated here. Flies (Diptera) often have wings covered in microtrichia – hair-like structures – that might create surface roughness that effects wettability. Roughened hydrophobic surfaces can become superhydrophobic, allowing water to easily be shed from the wings. Surface features of wings of flies from the families Apioceridae, Culicidae, Muscidae, Mydidae, Sarcophagidae, and Syrphidae were characterized with scanning electron microscopy (SEM). Goniometry was used to determine their wettability. SEM and goniometry revealed that there is a relationship between fly wing structures and wetting – those with hierarchies of nano- and microscale structures are able to achieve superhydrophobicity. Diffraction gratings, regular slits, grooves, or other structures with nano- or microscale spacing, have long been known to create iridescent beetle elytra or abdominal tergites. Beetles and other organisms with diffraction-grating induced iridescence tend to inhabit similar moist microhabitats and share burrowing behaviors. It has been hypothesized that these gratings effect friction and allow beetles to more easily move through substrates and that iridescence is a byproduct of this friction-reducing mechanism. Visual, water-shedding, and friction-reducing roles of this iridescence were examined in carabid, staphylinid, and scarab beetles. No differences were found in the ability to match the color of various substrates or to linearly polarize light between iridescent and noniridescent beetles. The ability for diffraction gratings to modify cuticle wettability varied among species and related to surface roughness that resulted from the gratings. Tribological measurements found that the presence or absence of diffraction gratings modifies friction in some beetles. The effect of diffraction gratings on friction interactions involves a tradeoff between increased friction and decreased wettability created by surface roughness resulting from diffraction gratings.
Issue Date:2019-07-15
Rights Information:Copyright 2019 Kristen Reiter
Date Available in IDEALS:2019-11-26
Date Deposited:2019-08

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