3 research outputs found
3D tomographic analysis of the order-disorder interplay in the Pachyrhynchus congestus mirabilis weevil
The bright colors of Pachyrhynchus weevils originate from complex dielectric
nanostructures within their elytral scales. In contrast to previous work
exhibiting highly ordered single-network diamond-type photonic crystals, we
here show by combining optical microscopy and spectroscopy measurements with 3D
FIB tomography that the blue scales of P. congestus mirabilis differ from that
of an ordered diamond structure. Through the use of FIB tomography on elytral
scales filled with Pt by electron beam-assisted deposition, we reveal that the
red scales of this weevil possess a periodic diamond structure, while the
network morphology of the blue scales exhibit diamond morphology only on the
single scattering unit level with disorder on longer length scales. Full wave
simulations performed on the reconstructed volumes indicate that this local
order is sufficient to open a partial photonic bandgap even at low dielectric
constant contrast between chitin and air in the absence of long-range or
translational order. The observation of disordered and ordered photonic
crystals within a single organism opens up interesting questions on the
cellular origin of coloration and studies on bio-inspired replication of
angle-independent colors.Comment: 13 pages, 10 figure
Rendering polyurethane hydrophilic for efficient cellulose reinforcement in melt-spun nanocomposite fibers
Many commodity plastics, such as thermoplastic polyurethanes (PUs), require reinforcement for use as commercial products. Cellulose nanocrystals (CNCs) offer a āgreenā and scalable approach to polymer reinforcement as they are exceptionally stiff, recyclable, and abundant. Unfortunately, achieving efficient CNC reinforcement of PUs with industrial melt processing techniques is difficult, mostly due to the incompatibility of the hydrophobic PU with hydrophilic CNCs, limiting their dispersion. Here, a hydrophilic PU is synthesized to achieve strong reinforcement in meltāprocessed nanocomposite fibers using filter paperāsourced CNCs. The meltāspun fibers, exhibiting smooth surfaces even at high CNC loading (up to 25 wt%) indicating good CNC dispersion, are benchāmarked against solventācast filmsāsolvent processing is not scalable but disperses CNCs well and produces strong CNC reinforcement. Mechanical analysis shows the CNC addition stiffens both nanocomposite films and fibers. The stress and strain at break, however, are not significantly affected in films, whereas adding CNCs to fibers increases the stressāatābreak while reducing the straināatābreak. Compared to earlier studies employing a hydrophobic (and stiffer) PU, CNC addition to a hydrophilic PU substantially increases the fiber stiffness and strength. This work therefore suggests that rendering thermoplastics more hydrophilic might pave the way for āgreenerā polymer composite products using CNCs
Anoplophora graafi Longhorn Beetle Coloration is due to Disordered Diamond-like Packed Spheres
While artificially photonic materials are typically highly ordered, photonic structures in many species of birds and insects do not possess a long-range order. Studying their order-disorder interplay sheds light on the origin of the photonic band gap. Here, we investigated the scale morphology of the Anoplophora graafi longhorn beetle. Combining small-angle X-ray scattering and slice-and-view FIB-SEM tomography with molecular dynamics and optical simulations, we characterised the chitin sphere assemblies within blue and green. A. graafi scales. The low volume fraction of spheres and the number of their nearest neighbours are incompatible with any known close-packed sphere morphology. A short-range diamond lattice with long-range disorder best describes the sphere assembly, which will inspire the development of new colloid-based photonic materials