• Dattani, Rajeev
• Villanova, Julie
• Mykhaylyk, Oleksandr
• Furnass, Will
• Hill, Christopher J.
• Jones, Richard A. L.
• Martin, Simon J.
• Coles, David M.
• Burg, Stephanie L.
• Parker, Andrew
• Ryan, Anthony J.
• Vukusic, Pete
• Parnell, Andrew J.
• Doak, Scott
• Prevost, Sylvain
• Bianco, Antonino
• Dennison, Andrew J. C.
• Croucher, Mike
• Dalgliesh, Robert
• Mcloughlin, Daragh
• Washington, Adam
• Hutchings, Mark
• Parnell, Steven R.
• Vasilev, Cvetelin
• Clarke, Nigel
• Fairclough, Patrick

Abstract

<jats:title>Abstract</jats:title><jats:p><jats:italic>Cyphochilus</jats:italic> 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 <jats:italic>Cyphochilus</jats:italic> and <jats:italic>Lepidiota stigma</jats:italic>. Chitin-filling fractions are found to be 31 ± 2% for <jats:italic>Cyphochilus</jats:italic> and 34 ± 1% for <jats:italic>Lepidiota stigma</jats:italic>, 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.</jats:p>

Topics

• density
• impedance spectroscopy
• polymer
• simulation
• spinodal decomposition
• liquid phase
• X-ray scattering