one of the most famous poems By Gerard Manley Hopkins He begins by praising the phenomenon of iridescence. It is represented by the colorful wings of king hunters and dragonflies in Hopkins’ poem, but iridescence can also be found in the wings of cicadas and butterflies, in certain species of beetles, and in the brightly colored feathers of male peacocks. Now, a team of researchers at the Massachusetts Institute of Technology has captured on video the unique skeletal growth of a butterfly’s wings — continuously, as the butterfly develops inside its cocoon — for the first time. The researchers describe their findings in a new paper published in the Proceedings of the National Academy of Sciences.
as I wrote beforeThe bright iridescent colors in a butterfly’s wings do not come from any pigment molecules but from how the wings are formed. It is a naturally occurring example of what physicists call Photonic crystals. The scales of chitin (a common polysaccharide in insects) are arranged like roof tiles. Basically, they make up a file diffraction grating, except that photonic crystals produce specific colors, or specific wavelengths of light, while diffraction gratings produce the entire spectrum, just like a prism.
Also known as optical bandgap materials, photonic crystals are “tunable,” meaning that they are precisely arranged in such a way that they block certain wavelengths of light while allowing others to pass through. Adjust the structure by changing the size of the tiles, and the crystals become sensitive to a different wavelength. (Actually, the rainbow weevil can be controlled Both the size of its scales and the amount of chitin used to adjust those colors as needed.)
Even better (from an application point of view), color perception does not depend on the viewing angle. And scales aren’t just for aesthetics; They help protect the insect from the elements. There are several types of Synthetic Photonics CrystalsBut gaining a better and more detailed understanding of how these structures grow in nature could help scientists design new materials with similar qualities, such as light-colored windows, self-cleaning surfaces for cars and buildings, or even waterproof textiles. Currency notes can include ciphered iridescent patterns to thwart counterfeiters.
Butterfly wings have long fascinated scientists, since the first documentation of said wing growth in 1938. We now have more advanced imaging techniques, shedding more light on this complex process. “Previous studies Presenting compelling shots at specific stages of development; Unfortunately, they do not reveal the ongoing timeline and sequence of what is happening as the scale structures grow,” Co-author Matthias Kohli said:, a mechanical engineer at MIT. “We needed to see more to start understanding it better.”
The team collected groups of painted butterflies (Vanessa CardoyIn the laboratory, carefully monitor larvae in individual containers until larvae have shed their skins. Once the caterpillars were encased in a cocoon and the final transformation into butterflies began, the researchers began recording the process. They relied on two surgical approaches to obtain an inside view of wing development in cocoons.
First, the researchers exposed the anterior portion of the skin by removing a portion of the cuticle with a scalpel; Cocoons were anesthetized for this procedure. They then placed a thin glass cover over the excised area using bio-adhesive and sealed it with a portable dental light treatment lamp.
To photograph the hind wings, the MIT team grabbed both the cuticle of the cocoon and the frontal suture and twisted them toward the head. The aft and aft wing were separated by a strip of dental compound. Again, the researchers used a cover glass to protect the exposed wing and provide a window into the cocoon, sealing the window in place with dental compound.
However, the researchers needed a special type of imaging to capture the formation of the wing, as simply shining a wide beam of light onto the wing can damage cells. The solution: speckle-bonding phase reflection microscopy, which involves shining many small points of light at specific points on the wing.
“The spotted field is like thousands of fireflies generating a field of light points,” Co-author Peter Su said, one of three experts in this type of imaging who collaborated on experiments. “Using this method, we can isolate the light coming from different layers, and we can reconstruct the information to effectively map a three-dimensional structure.”