JAN 19, 2016 11:54 PM PST

Engineers use fractals to mimic ‘metallic' fish skin

The shiny skins of certain ribbonfish reflect light across a broad range of wavelengths, giving them a brilliant metallic appearance.

The reflectivity is the result of stacked layers of crystalline organic compounds embedded in their skin’s cytoplasm. Some organisms with metallic sheens have layers that are stacked in a regular pattern, while others, including the ribbonfish, have stacking patterns described as “chaotic” or random.
 
"There is an underlying pattern, but there is randomness built in," says Jeremy Bossard, "similar to the way that living trees have an overall fractal pattern but do not grow symmetrically."

Researchers determined that the stacking is not completely random and developed mathematical algorithms to replicate those patterns in semiconductor materials.

“We are proposing a model that uses fractal geometry to describe the layering in the biological structure of silvery fish,” says Jeremy Bossard, postdoctoral researcher in electrical engineering at Penn State. “While we are not trying to reproduce the structure found in nature, the same model could guide the design of devices such as broadband mirrors.”

Fractals have been called the “geometry of nature” because they can help describe the irregular but self-similar patterns that occur in natural objects such as branching tree limbs.

The researchers use a one-dimensional fractal, known as a Cantor bar fractal, which is a line divided by spaces or gaps. Normally, Cantor fractals appear to be very regular, but when random changes are introduced to the geometry, a more complex pattern emerges. The pattern resembles the layering of reflective layers in ribbonfish skin.

“There is an underlying pattern, but there is randomness built in,” says Bossard, “similar to the way that living trees have an overall fractal pattern but do not grow symmetrically.”

The researchers then use another nature-inspired computational method called a genetic algorithm that mimics Darwinian evolution to create successive generations of fractal patterns from the parent patterns. Over approximately 100 generations, the patterns converge on the best design to meet all the target requirements.

Using fractals and the genetic algorithm, the researchers were able to mathematically generate patterns targeting optical functions in the mid-infrared and near-infrared ranges, including broadband reflection.
They propose that the design approach could be used to develop nanoscale stacks with customized reflective spectra. The research results are reported in the Journal of the Royal Society Interface.

The National Science Foundation’s Center for Nanoscale Science and Penn State supported the work.

This article originally published on futurity.org.
About the Author
  • Futurity features the latest discoveries by scientists at top research universities in the US, UK, Canada, Europe, Asia, and Australia. The nonprofit site, which launched in 2009, is supported solely by its university partners (listed below) in an effort to share research news directly with the public.
You May Also Like
MAR 11, 2021
Chemistry & Physics
More effective way of recycling carbon fibers
MAR 11, 2021
More effective way of recycling carbon fibers
A team from the University of Sydney's School of Civil Engineering has designed a method to improve the recycling of ...
MAR 24, 2021
Chemistry & Physics
Can we promote the hydrogen economy without fossil fuels?
MAR 24, 2021
Can we promote the hydrogen economy without fossil fuels?
New research published in Angewandte Chemie International Edition reports a novel approach to producing hydrogen su ...
MAY 05, 2021
Chemistry & Physics
Chemical nose sniffs out DNA irregularities
MAY 05, 2021
Chemical nose sniffs out DNA irregularities
A new study published in the journal Nature Chemistry details the development of a chemical nose that can identify ...
MAY 21, 2021
Space & Astronomy
Alien Radioactive Element Discovered on Earth for First Time
MAY 21, 2021
Alien Radioactive Element Discovered on Earth for First Time
  Researchers from Australian National University have discovered the first ever extraterrestrial radioactive isoto ...
JUL 09, 2021
Space & Astronomy
Cluster of Free-Floating Planets Captured by Kepler Telescope
JUL 09, 2021
Cluster of Free-Floating Planets Captured by Kepler Telescope
The Kepler Space Telescope has captured evidence of mysterious free-floating planets, or planets that are alone in deep ...
JUL 19, 2021
Cell & Molecular Biology
ATP & GTP Are Common in Biology - But What About CTP?
JUL 19, 2021
ATP & GTP Are Common in Biology - But What About CTP?
Adenosine triphosphate (ATP) is a molecule that provides crucial energy to activate a wide array of biological processes ...
Loading Comments...