Tuesday, October 21, 2014

Physics reveals how nature sparkles


Researchers from the University of Bristol have revealed 'a universal explanation' for many of the dazzling coloured and silvery reflections in the natural world.


The team revealed that disordered layers of crystals that are responsible for silvery reflective scales of fish reflect light in the same way as coloured, iridescent insect wings and carapaces.


The research reveals just how shiny creatures have evolved nanoscale structures that exploit light.


The team also says that humans could copy the effect to produce, for example, hyper-reflective surfaces.


Their research is published in the Royal Society journal Interface.


The very silvery scales of fish, like sardines and herring, are made up of microscopic layers of crystals.


'What's important is that the crystals have a range of different thicknesses,' said Dr Tom Jordan, a member of the research team.



Different amounts of this nano-scale disorder is found in the surface of fish scales, butterfly wings and beetle carapaces, and produces an effect known as Anderson localisation.


This a physical phenomenon whereby disorder can prevent light waves from propagating through a material.


'As the light [wave] goes in and meets these changes in the different layers, the multiple waves all interfere with with each other,' lead scientist on the study, Dr Nicholas Roberts, explained.


This means the light waves 'bounce around inside the layers' and are eventually reflected back out. These surfaces reflect more light than many man-made structures, producing colourful metallic iridescence or dazzling silver shine that we see in the natural world.


'Disorder within both types means that it's the same optical property that causes the coloured and silvery surfaces [to shine],' explained Dr Roberts.


He added that the structures could be copied to produce highly reflective surfaces to, for example, manufacture reflectors to make LED lights more efficient.


This is why we find science exciting,' he said.


'[We can] look at nature to find things we haven't even thought of.'


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