ScienceDaily (Oct. 9, 2009) — A
team of researchers from the State University of Pennsylvania (USA) and
the Universidad Autónoma de Madrid (UAM) has developed a technique to
replicate biological structures, such as butterfly wings, on a nano
scale. The resulting biomaterial could be used to make optically active
structures, such as optical diffusers for solar panels.
Insects' colours and their iridescence (the ability to change
colours depending on the angle) or their ability to appear metallic are
determined by tiny nano-sized photonic structures (1 nanometre = 10-9
m) which can be found in their cuticle. Scientists have focused on
these biostructures to develop devices with light emitting properties
that they have just presented in the journal Bioinspiration & Biomimetics.
"This technique was developed at the Materials Research Institute of
the State University of Pennsylvania and it enables replicas of
biological structures to be made on a nanometric scale", Raúl J.
Martín-Palma, lecturer at the Department of Applied Physics of the UAM
and co-author of the study explains.
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.
Martín-Palma points out 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 maximise solar cell light absorption, or other types of
devices. "Furthermore, the technique can be used to replicate other
biological structures, such as beetle shells or the compound eyes of
flies, bees and wasps," the researcher says.
The compound eyes of certain insects are sound candidates for a
large number of applications as they provide great angular vision. "The
development of miniature cameras and optical sensors based on these
organs would make it possible for them to be installed in small spaces
in cars, mobile telephones and displays, apart from having uses in
areas such as medicine (the development of endoscopes) and security
(surveillance)", Martín-Palma says.
- Akhlesh Lakhtakia, Raúl J. Martín-Palma, Michael A. Motyka y Carlo G. Pantano. Fabrication of free-standing replicas of fragile, laminar, chitinous biotemplates. Bioinspiration & Biomimetics, 2009; 4 (3): 034001
Adapted from materials provided by FECYT - Spanish Foundation for Science and Technology, via EurekAlert!, a service of AAAS.