Feeling the heat (Image: Patrick Landmann/Science Photo Library)
Move over spider silk. Butterfly wings are the new "it" material of the animal kingdom, doubling up as ultra-sensitive heat sensors.
Morpho
butterfly wings are iridescent thanks to rows of tiny tree-like
structures on their surfaces. Light reflecting off each micrometre-long
branch and trunk interferes, producing shimmering colours.
Now Andrew Pris at General Electric's Global Research Center in Niskayuna, New York, and colleagues say those same "Christmas trees" make excellent heat sensors.
When
heat, or infrared radiation, hits the trees, the chitin they are made
from expands. This increases the distance between the branches and
trunks, shifting the wavelength of light they reflect perceptibly.
To
boost the wings' sensitivity, the researchers coated samples with a
layer of heat-absorbing carbon nanotubes. The coated wings could reveal
temperature differences of just 0.018 °C.
Miniaturised beauty
"The
beauty of the system described in the paper is its outstanding
miniaturisation," says Helmut Schmitz of the University of Bonn in
Germany.
The
distances between the tree trunks determine the sensors' spatial
resolution. At less than a micrometre, this resolution is more than 20
times as sharp as existing detectors. The trees' diminutive size, along
with chitin's properties, also means they heat up and cool down very
quickly, allowing them to respond to small and fleeting changes in
temperature, says team leader Radislav Potyrailo, also at General
Electric.
One day, Morpho-inspired sensors could detect inflamed areas in people, or points of friction in machines, the team say.
Does
Potyrailo think physics has now bested the butterfly? Not at all, he
says: "We can maybe touch one aspect of their performance, but other
aspects are still quite remarkable."
Journal reference: Nature Photonics, DOI: 10.1038/nphoton.2011.355
http://www.newscientist.com/
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