Diverse forms of nanoscale architecture generate structural colour and perform signalling functions within and between species. Structural colour is the result of the interference of light from approximately regular periodic structures; some structural disorder is, however, inevitable in biological organisms. Is this disorder functional and subject to evolutionary selection, or is it simply an unavoidable outcome of biological developmental processes? Here we show that disordered nanostructures enable flowers to produce visual signals that are salient to bees. These disordered nanostructures (identified in most major lineages of angiosperms) have distinct anatomies but convergent optical properties; they all produce angle-dependent scattered light, predominantly at short wavelengths (ultraviolet and blue). We manufactured artificial flowers with nanoscale structures that possessed tailored levels of disorder in order to investigate how foraging bumblebees respond to this optical effect. We conclude that floral nanostructures have evolved, on multiple independent occasions, an effective degree of relative spatial disorder that generates a photonic signature that is highly salient to insect pollinators.

Cellulose nanocrystals in water suspensions behave as lyotropic liquid crystals forming a chiral nematic phase above a critical concentration. Such an organization can be retained in solid films and give rise to an intense colored appearance. Here, we characterize their optical response by applying optical and scanning electron microscopy, imaging scatterometry, and angle-resolved reflectance measurements. We show that the experimental results are well explained by computational modeling using the finite-difference time-domain method, but slightly less well by Berremann’s analytical model.

Anharmonic crystal lattice dynamics have been observed in lead halide perovskites on picosecond timescales. Here, we report that the soft nature of the perovskite crystal lattice gives rise to dynamic fluctuations in the electronic properties of excited states. We use linear polarization selective transient absorption spectroscopy to study the charge carrier relaxation dynamics in lead-halide perovskite films and nanocrystals. We find that photo-excited charge carriers maintain an initial polarization anisotropy for several picoseconds, independent of crystallite size and composition, and well beyond the reported timescales of carrier scattering. First-principles calculations find intrinsic anisotropies in the transition dipole moment, which depend on the orientation of light polarization and the polar distortion of the local crystal lattice. Lattice dynamics are imprinted in the optical transitions and anisotropies arise on the time-scales of structural motion. The strong coupling between electronic states and structural dynamics requires a unique interpretation of recombination and transport mechanisms.

Viburnum tinus is an evergreen shrub that is native to the Mediterranean region but cultivated widely in Europe and around the world. It produces ripe metallic blue fruits throughout winter [1]. Despite its limited fleshy pulp,[2] its high lipid content[3] makes it a valuable resource to the small birds[4] that act as its seed-dispersers [5]. Here, we find that the metallic blue appearance of the fruits is produced by globular lipid inclusions arranged in a disordered multilayer structure. This structure is embedded in the cell walls of the epicarp and underlaid with a dark layer of anthocyanin pigments. The presence of such large, organised lipid aggregates in plant cell walls represents a new mechanism for structural colouration and may serve as an honest signal of nutritional content. 639088 (S.V., Y.O., G.J.), a microMORPH Cross-Training Grant (M.S.A.), a Yale Institute for Biospheric Studies grant (M.S.A.), National Science Foundation (NSF)SF GRFP DGE-1122492 (M.S.A.), and NSF DBI 1907293 (M.S.A.). We would like to acknowledge the assistance of the Boulder Electron Microscopy Service in preparation and imaging the serial block-face, and the support of the Cambridge Advanced Imaging Centre and the NanoBio-ICMG platform (FR 2607) electron microscopy facility. We are grateful to Heather Whitney and Innes Cuthill for loan of equipment and to two anonymous referees for advice and comments which improved the manuscript.

Solution‐based near‐field electrospinning is employed to construct polymeric network membranes, made of orderly arranged and interconnected fibers. The narrow tip‐to‐nozzle separation of the direct‐writing process leads to solvent enriched fibers being deposited on the substrate, despite the use of a low boiling point solvent. This results in fibers with low cross‐sectional aspect ratio (flattened appearance), but providing a unique opportunity to produce interconnected fiber junctions through in situ, localized solvent etching by subsequent fiber overlays. Orthogonal networks of polycaprolactone (PCL) fibres, or PCL/collagen composite fibres, are fabricated, and then characterized by microscopy and spectroscopy techniques. This study presents a direct approach to strengthen interfiber junctions, and further the feasibility to interweave and interconnect fibers of different properties, leading to networked membranes with potentially tailorable functions for tissue engineering applications and beyond.