Disordered Cellulose-based Nanostructures for Enhanced Light-scattering

Cellulose is the most abundant bio-polymer on earth. Cellulose fibres, such as the one extracted form cotton or woodpulp, have been used by humankind for hundreds of years to make textiles and paper. Here we show how, by engineering light matter-interaction, we can optimise light scattering using exclusively cellulose nanocrystals. The produced material is sustainable, biocompatible and, when compared to ordinary microfibre-based paper, it shows enhanced scattering strength (x4) yielding a transport mean free path as low as 3.5 um in the visible light range. The experimental results are in a good agreement with the theoretical predictions obtained with a diffusive model for light propagation

The influence of pigmentation patterning on bumblebee foraging from flowers of <em>Antirrhinum majus</em>

Patterns of pigmentation overlying the petal vasculature are common in flowering plants,and have been postulated to play a role in pollinator attraction. Previous studies report that such venation patterning is significantly more attractiveto bee foragers in the field than ivory or white flowers without veins. To dissect the ways in which venation patterning of pigment can influence bumblebee behaviour we investigated the response of flower-naïve individuals of Bombus terrestris to veined, ivory and red near-isogenic lines of Antirrhinum majus. We find that red venation shifts flower colour slightly, although the ivory background is the dominant colour. Bees were readily able to discriminate between ivory and veined flowers under differential conditioning, but showed no innate preference when presented with a free choice of rewarding ivory and veined flowers. In contrast, both ivory and veined flowers were selected significantly more often than were red flowers. We conclude that advantages conferred by venation patterning might stem from bees learning of their use as nectar guides, rather than from any innate preference for striped flowers. </p

Flexible Photonic Cellulose Nanocrystal Films.

The fabrication of self-assembled cellulose nanocrystal (CNC) films of tunable photonic and mechanical properties using a facile, green approach is demonstrated. The combination of tunable flexibility and iridescence can dramatically expand CNC coating and film barrier capabilities for paints and coating applications, sustainable consumer packaging products, as well as effective templates for photonic and optoelectronic materials and structures.CelluForce Inc., Biotechnology and Biological Sciences Research Council (David Phillips fellowship (Grant ID: BB/K014617/1, 76933), European Research Council (Grant ID: ERC-2014-STG H2020 639088), Engineering and Physical Sciences Research Council (Grant ID: 1525292

Optical properties of gyroid structured materials: from photonic crystals to metamaterials

This is the accepted manuscript. The final version is available from Wiley at http://onlinelibrary.wiley.com/doi/10.1002/adom.201400333/abstract.The gyroid is a continuous and triply periodic cubic morphology which possesses a constant mean curvature surface across a range of volumetric fill fractions. Found in a variety of natural and synthetic systems which form through self-assembly, from butterfly wing scales to block copolymers, the gyroid also exhibits an inherent chirality not observed in any other similar morphologies. These unique geometrical properties impart to gyroid structured materials a host of interesting optical properties. Depending on the length scale on which the constituent materials are organised, these properties arise from starkly different physical mechanisms (such as a complete photonic band gap for photonic crystals and a greatly depressed plasma frequency for optical metamaterials). This article reviews the theoretical predictions and experimental observations of the optical properties of two fundamental classes of gyroid structured materials: photonic crystals (wavelength scale) and metamaterials (subwavelength scale).This work was supported by the EPSRC through the Cambridge NanoDTC EP/G037221/1, EP/G060649/1, EP/L027151/1, and ERC LINASS 320503

Bright-white beetle scales optimise multiple scattering of light.

Whiteness arises from diffuse and broadband reflection of light typically achieved through optical scattering in randomly structured media. In contrast to structural colour due to coherent scattering, white appearance generally requires a relatively thick system comprising randomly positioned high refractive-index scattering centres. Here, we show that the exceptionally bright white appearance of Cyphochilus and Lepidiota stigma beetles arises from a remarkably optimised anisotropy of intra-scale chitin networks, which act as a dense scattering media. Using time-resolved measurements, we show that light propagating in the scales of the beetles undergoes pronounced multiple scattering that is associated with the lowest transport mean free path reported to date for low-refractive-index systems. Our light transport investigation unveil high level of optimisation that achieves high-brightness white in a thin low-mass-per-unit-area anisotropic disordered nanostructure.The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007–2013)/ERC grant agreement n [291349] and USAF grant FA9550-10-1-0020.This is the final published version, also available from Nature Publishing at http://www.nature.com/srep/2014/140815/srep06075/full/srep06075.html

Structural colour from helicoidal cell-wall architecture in fruits of Margaritaria nobilis

The bright and intense blue-green coloration of the fruits of Margaritaria nobilis (Phyllanthaceae) was investigated using polarization-resolved spectroscopy and transmission electron microscopy. Optical measurements of freshly collected fruits revealed a strong circularly polarized reflection of the fruit that originates from a cellulose helicoidal cell wall structure in the pericarp cells. Hyperspectral microscopy was used to capture the iridescent effect at the single-cell level.Leverhulme Trust (F/09-741/G)United States. Air Force Office of Scientific Research (award number FA9550-10-1-0020)Adolphe Merkle FoundationSwiss National Science Foundation (National Centre of Competence in Research Bio-Inspired Materials)Biotechnology and Biological Sciences Research Council (Great Britain) (BBSRC David Phillips fellowship (BB/K014617/1)