Researchers at the Universidad Auti³noma de Madrid (UAM) and the State University of Pennsylvania (USA) have created a method to replicate biological structures, such as butterfly wings, on a nanometric scale. The resulting biomaterial could be used to make optically active structures, such as optical diffusers for solar panels.
The insects’ colors and their iridescence (the ability to change colors depending on the angle) or their ability to appear metallic are determined by tiny nano-sized photonic structures (1 nanometre = 10-9 m) that can be found in their cuticle. Researchers have focused on these bio-structures to develop devices with light emitting properties.
The researchers have created “free-standing replicas of fragile, laminar, chitinous biotemplates”, that is, copies of the nano structures of butterfly wings. The appearance of these appendices usually depends more on their periodical nanometric structure (which determines the “physical” colour) than on the pigments in the wings (which establish the “chemical” colour).
In order to create new biomaterial, the team used compounds based on Germanium, Selenium and Stibium (GeSeSb) and employed a technique called Conformal-Evaporated-Film-by-Rotation (CEFR), which combines thermal evaporation and substrate rotation in a low pressure chamber. They also used immersion in an aqueous orthophosphoric acid solution to dissolve the chitin (substance typically found in the exoskeleton of insects and other arthropods).
The methods used to date to replicate bio structures are very limited when it comes to obtaining effective copies on a nanometric scale and they often damage the original biostructure because they are used in corrosive atmospheres or at high temperatures. The new technique “totally” overcomes these problems, as it is employed at room temperature and does not require the use of toxic substances.
Martin-Palma, lecturer at the Department of Applied Physics of the UAM, explains that the structures resulting from replicating the biotemplate of butterfly wings could be used to make various optically active structures, such as optical diffusers or coverings that maximize solar cell light absorption, or other types of devices. According to the researchers, “the technique can be used to replicate other biological structures, such as beetle shells or the compound eyes of flies, wasps and bees.” The compound eyes of certain insects are sound candidates for a large number of applications as they provide great angular vision.