Liquid – liquid phase separation morphologies in ultra-white beetle scales and a synthetic equivalent
journal contributionposted on 02.09.2019 by Stephanie L Burg, Adam Washington, David M Coles, Antonino Bianco, Daragh Mcloughlin, Oleksandr O Mykhaylyk, Julie Villanova, Andrew JC Dennison, Christopher J Hill, Pete Vukusic, Scott Doak, Simon Martin, Mark Hutchings, Steven R Parnell, Cvetelin Vasilev, Nigel Clarke, Anthony J Ryan, Will Furnass, Mike Croucher, Robert M Dalgliesh, Sylvain Prevost, Rajeev Dattani, Andrew Parker, Richard AL Jones, J Patrick A Fairclough, Andrew J Parnell
Any type of content formally published in an academic journal, usually following a peer-review process.
Cyphochilus beetle scales are amongst the brightest structural whites in nature, being highly opacifying whilst extremely thin. However, the formation mechanism for the voided intra- scale structure is unknown. Here we report 3D x-ray nanotomography data for the voided chitin networks of intact white scales of Cyphochilus and Lepidiota stigma. Chitin-filling frac- tions are found to be 31 ± 2% for Cyphochilus and 34 ± 1% for Lepidiota stigma, indicating previous measurements overestimated their density. Optical simulations using finite- difference time domain for the chitin morphologies and simulated Cahn-Hilliard spinodal structures show excellent agreement. Reflectance curves spanning filling fraction of 5-95% for simulated spinodal structures, pinpoint optimal whiteness for 25% chitin filling. We make a simulacrum from a polymer undergoing a strong solvent quench, resulting in highly reflective ( 94%) white films. In-situ X-ray scattering confirms the nanostructure is formed through spinodal decomposition phase separation. We conclude that the ultra-white beetle scale nanostructure is made via liquid–liquid phase separation.
Innovate UK (Grant Number 33692-239251) in partnership with AkzoNobel and the University of Sheffield
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