While I was in New York a few weeks ago I stopped by the American Museum of Natural History – mostly in order to pay a visit to @NatHistoryWhale – which, in case you’re not familiar, is a 1:1 replica of a blue whale hanging from the ceiling.  As I went to enter the gigantic hall of enormous ocean life I stopped short to examine a back-lit wall bedazzled with a fascinating array of taxidermied creatures including a 7 pound lobster from New Jersey. 

Images courtesy amnh.org and vipnyc.org 

Pinned up along one side of the wall was a row of brilliantly colored butterflies.  They were so glittery and shiny and their patterns so vivid in color that I wanted to sew a coat out of their wings and wear it for the rest of my life.  But I abandoned the idea, reasoning that the colors would probably fade with time and also because a coat made of insect parts is gross.

Fast forward to today and the butterfly wing coat idea is still gross.  However, I did find out that the colors on butterfly wings don’t fade because … wait for it … they are made of crystal nanostructures called gyroids.  “These are ‘mind-bendingly weird’ three-dimensional curving structures that selectively scatter light,” according to Richard Prum, chair and the William Robertson Coe Professor in the Department of Ornithology, Ecology and Evolutionary Biology at Yale (Source: Physorg.com). Geometrically speaking, a gyroid is “an infinitely connected triply periodic minimal surfacediscovered by Alan Schoen in 1970″ (Wikipedia) and it’s highly awesome.  You can think of it as a network of “three bladed boomerangs” if that helps (Physorg.com). 

Image courtesy Wikipedia

The gyroids on butterfly wings are made of chitin, which is a tough starchy material that forms the exterior of insects and crustaceans.  The chitin that makes up the exoskeletons of crabs and scorpions is typically deposited on the outer membranes of cells, and it doesn’t usually take the form of a gyroid. 

The Yale research team used an X-ray scattering technique at the Argonne National Laboratory in Illinois to determine that, “essentially, the outer membranes of the butterfly wing scale cells grow and fold into the interior of the cells. The membranes then form a double gyroid — or two, mirror-image networks shaped by the outer and inner cell membranes. The latter are easier to grow but are not as good at scattering light. Chitin is then deposited in the outer gyroid to create a single solid crystal. The cell then dies, leaving behind the crystal nanostructures on the butterfly wing” (Physorg.com). 

Okay, so the crystal nanostructures come in pretty colors and they’re durable.  But the most exciting aspect of this line of research has to do with solar cells.  Gyroid shapes can improve the efficiency of solar cells and other optical devices. 

Image Credit: Michael Apel, Wikipedia Commons

Researcher Di Zhang and colleagues are turning to the microscopic solar scales on butterfly wings in their search for materials that may improve the already high efficiency of light-harvesting in dye-sensitized solar cells, also known as Grätzel cells after inventor Michael Grätzel. These solar cells can convert 10% of the light energy that strikes them into electricity (Source: ACS). 

Di Zhang and co. used natural butterfly wings as a mold or template to make copies of the solar collectors, and transferred those light-harvesting structures to Grätzel cells. “Laboratory tests showed that the butterfly wing solar collector absorbed light more efficiently than conventional dye-sensitized cells. The fabrication process is simpler and faster than other methods, and could be used to manufacture other commercially valuable devices, the researchers say” (ACS).  The more efficient our solar cells become, the fewer of them we’ll need to manufacture – meaning less waste, less space, less time, and more betterness.

WU XING:

I’m always distracted by things that are shiny. I’m placing this post in the fire category.

Cited:

“Novel Photoanode Structure Templated from Butterfly Wing Scales”, Chemistry of Materials. Provided by ACS via Physorg.com.  Accessed 06/15/10.  URL.

“Colors of Butterfly Wing Yield Clues to Light-Altering Structures” Provided by Yale University via Physorg.com.  Accessed 06/15/10.  URL.