Anoplophora graafi longhorn beetle coloration is due to disordered diamond-like packed spheres
Abstract
While artificial photonic materials are typically highly ordered, biological photonic structures often lack long-range order. We here show that the colours of the scales of a longhorn beetle arise from a non-close-packed, diamond-coordinated assembly of 200-nm-sized chitin spheres. While artificial 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.
- Publication:
-
Soft Matter
- Pub Date:
- March 2024
- DOI:
- 10.1039/D4SM00068D
- arXiv:
- arXiv:2309.14177
- Bibcode:
- 2024SMat...20.2509D
- Keywords:
-
- Physics - Optics;
- Physics - Biological Physics