Researchers at Shanghai Jiaotong University are working on a black surface that maximizes absorption of light, resulting in a more efficient solar energy technology. The surface mimics the black portions of the winges of the green birdwing butterfly, using an ultrathin and super black amorphous carbon (a-C) film. Amorphous carbon (a-C) is a carbonaceous solid that has no long-range crystalline order, and usually contains hydrogen and nitrogen. This material should overcome the limitations of the butterfly's wing material, made up of a chitin/melanin composite. They have built a model to harness solar power the same way the butterflies’ wings do, and plan to create a commerical product.
"The biomimetic a-C film shows good optical absorption (99%) at low reflectance (<1%) in visible light (380–795 nm), which is comparable to the previously fabricated darkest materials, while with a thickness (5 lm) of only 15% of those materials."Source: Zhao Q; Fan T; Dina J; Zhang D; Guo Q; Kamada M. 2010. Super black and ultrathin amorphous carbon film inspired by anti-reflection architecture in butterfly wing. Carbon. 49(3): 877-883.
Research on the green birdwing butterfly, Ornithoptera priamus, inspired the researchers to further study the structure of the black area of the butterfly's wings. They found that the overlapping scales of the wings are mainly comprised of adjacent inverse V-type ridges, which can effectively reduce reflection, while at the same time keep transmission at a relatively low level. Because of the almost complete absorption of light, the wings form a model for more efficient solar energy collection.
Current solar technology has a lot of inefficiency. Dye-sensitized solar cells use pigments to enhance light absorption. This new technology is looking at surface structure to perform the same function. The biomimetic a-C film tested by the researchers is not only stable and corrosion resistant but also flexible due to the noncrystalline structure and graphic bonds of amorphous carbon. This makes it a promising anti-reflection coating for various fields such as optical instruments, sensors and thermal detectors, and solar cells.Edit Summary