Antonino Bianco, PhD

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 fractions are found to be 31 ± 2% for Cyphochilus and 34 ± 1% for Lepidiota stigma, indicating previous measurements overestimated their… Show more

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 fractions 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. Show less

Titanium dioxide is the main white pigment used in the paint industry. It is the most efficient broad-band light scattering material due to the high refractive index and its ability to scatter light across the entire visible range of the electromagnetic spectrum. However, the high production costs and the high carbon footprint associated with this compound constitute a motivation for investigating alternative materials. Polymeric particles have the potential to become a competitive alternative… Show more

Titanium dioxide is the main white pigment used in the paint industry. It is the most efficient broad-band light scattering material due to the high refractive index and its ability to scatter light across the entire visible range of the electromagnetic spectrum. However, the high production costs and the high carbon footprint associated with this compound constitute a motivation for investigating alternative materials. Polymeric particles have the potential to become a competitive alternative considering both their physical properties and the comparatively low production costs. The objective of this work was the identification of a simple and cost effective system for the production of bio-mimetic multi-voided polymeric particles, to be introduced in paint formulation as a partial replacement for the industrial white material titanium dioxide.
Nature does not rely on titanium dioxide to produce striking examples of white and is particularly ingenious in designing structures that are capable of maximising the amount of scattering in very little material, producing a remarkable white in very thin tissues. Some of the most relevant structures displaying exceptional white are the scales of the Cyphochilus and Lepidiota stigma beetles, consisting of isotropic networks of rod-like filaments of chitin and air-filled voids, and the foam-like structures found in the feathers of the Garrulus glandarius (Eurasian jay) bird, consisting in spherical air-filled voids within a keratin matrix. Those were identified as the target structures for the synthetic work. An effective way of producing porous structures in polymer materials is based on the possibility of inducing phase separation in an initially homogeneous polymer solution. The phase separation process can be initiated by the introduction of a non-solvent (NIPS) into the system and can proceed by a mechanism of nucleation and growth or by spinodal decomposition. Show less

Porous polystyrene microspheres were produced by a process of nonsolvent induced phase separation (NIPS) from ternary polymer–solvent–nonsolvent (polystyrene–toluene–ethanol) systems and characterized by scanning electron microscopy (SEM) and small-angle X-ray scattering (SAXS) techniques. This study provides evidence for a link between the structural morphology of the porous polystyrene particles and the polystyrene concentration in the initial solutions. A reciprocal relationship between pore… Show more

Porous polystyrene microspheres were produced by a process of nonsolvent induced phase separation (NIPS) from ternary polymer–solvent–nonsolvent (polystyrene–toluene–ethanol) systems and characterized by scanning electron microscopy (SEM) and small-angle X-ray scattering (SAXS) techniques. This study provides evidence for a link between the structural morphology of the porous polystyrene particles and the polystyrene concentration in the initial solutions. A reciprocal relationship between pore diameter and polymer concentration was observed for the systems with the polymer amount below the critical chain overlap concentration, C*. Above C*, this relationship breaks down. The reciprocal relationship between porosity and polymer concentration can be used to facilitate the fine control of the void size. We demonstrate that the observed reciprocal relationship between pore diameter and polymer concentration correlates well with the relative amount of nonsolvent present in the system at the onset of the phase separation process. The pore size can be reduced and, consequently, the pore surface area can be increased either by reducing the polymer concentration in the initial solution or by decreasing the polymer molecular weight in the sample composition. Show less

Eurasian Jay feathers display periodic variations in the reflected colour from white through light blue, dark blue and black. We find the structures responsible for the colour are continuous in their size and spatially controlled by the degree of spinodal phase separation in the corresponding region of the feather barb. Blue structures have a well-defined broadband ultra-violet (UV) to blue wavelength distribution; the corresponding nanostructure has characteristic spinodal morphology with a… Show more

Eurasian Jay feathers display periodic variations in the reflected colour from white through light blue, dark blue and black. We find the structures responsible for the colour are continuous in their size and spatially controlled by the degree of spinodal phase separation in the corresponding region of the feather barb. Blue structures have a well-defined broadband ultra-violet (UV) to blue wavelength distribution; the corresponding nanostructure has characteristic spinodal morphology with a lengthscale of order 150 nm. White regions have a larger 200 nm nanostructure, consistent with a spinodal process that has coarsened further, yielding broader wavelength white reflectance. Our analysis shows that nanostructure in single bird feather barbs can be varied continuously by controlling the time the keratin network is allowed to phase separate before mobility in the system is arrested. Dynamic scaling analysis of the single barb scattering data implies that the phase separation arrest mechanism is rapid and also distinct from the spinodal phase separation mechanism i.e. it is not gelation or intermolecular re-association. Any growing lengthscale using this spinodal phase separation approach must first traverse the UV and blue wavelength regions, growing the structure by coarsening, resulting in a broad distribution of domain sizes. Show less