Structured nanocrystals revealed for the first time
Nature’s intricate mechanism for forming the nanostructures that help a butterfly species to camouflage itself against common leaves, has been revealed by researchers.
Investigation of nanostructures with non-destructive X-ray microscopes
In an international collaboration, Dr Gerd Schroeder-Turk from Murdoch University and Dr Bodo Wilts from the Adolphe Merkle Institute at the University of Fribourg in Switzerland, used 3D X-ray microscopy from ZEISS to investigate the nanostructure on the wing scales of the green Hairstreak butterfly. What they found on each wing scale were structured nanocrystals that were surprisingly not interconnected. Rather they were a series of regularly spaced points where so-called gyroid photonic structures had grown. Gyroids are labyrinth-like three-dimensional structures. These structures, which are partially pigmented, are responsible for the butterfly’s green color.
This was the first time this pattern was observed in butterflies, which are known for their particularly diverse wing scale structures. These structures are important to the insects for multiple functions such as signaling and water repellency. How the complex structures develop remains to this day largely unknown since it is impossible to observe on living specimens.
Learning from the mechanisms nature employs to make these structures
The researchers found out that the structure they observed grew in a multistep process. In a first stage, an enveloping casing or mold develops. Then it is filled by a biopolymeric gyroid structure with a different chemical composition. The results give insights into how butterfly wing cells develop, but could also provide inspiration for new nanoscale assembly techniques.