Fish skin points to better LEDs
Scaly secret to camouflage, and that's no red herring
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A trick of the light evolved by silvery fish to avoid predators could help improve optical devices like LEDs, according to a study in Nature Photonics.
While polarisation has many applications in photonics, non-polarising devices are also important. The research – abstract here – took a look at how fish such as sardines and herring reflect light without polarising it.
PhD student Tom Jordan from the Bristol Centre for Complexity Sciences, and his supervisors Professor Julian Partridge and Dr Nicholas Roberts in Bristol's School of Biological Sciences, found that these fish avoid reflecting polarised light by having two types of reflective crystals in their skins.
The crystals are guanine, which as Discovery points out is also a component of guano. A single guanine crystal layer in the scales would polarise the light reflected, which would also “dim” the reflected light.
However, with two types of guanine crystal in their skins, the light isn’t polarised. The resulting higher reflectivity is a defence against predators, as Dr Roberts explained: “We believe these species of fish have evolved this particular multilayer structure to help conceal them from predators, such as dolphin and tuna.
"These fish have found a way to maximize their reflectivity over all angles they are viewed from. This helps the fish best match the light environment of the open ocean, making them less likely to be seen.”
In photonics, this property could be used to make more efficient low-loss devices and brighter LED lamps, the researchers say. ®
COMMENTS
Re: Offroad lights
'tis a pity the police won't ticket motorists for having blinding lights (or badly adjusted lights, or failed lights)
Particularly those hateful DLRs which are now compulsory on new cars - and they are REALLY badly dazzling.
Sonar
A happy side-effect of the dual-crystal scales is that it scatters the acoustic frequencies that dolphins use to locate prey, rendering them invisible to sonar as well (aka stealth-scales).
The world-wide collapse in sardine populations does not represent a collapse at all - they have just evolved to hide better from us, since fishing boats also use sonar to locate schools of sardines.
It also protects the silvery fish against lasers, causing a massive collapse in the population of frikken sharks with frikken lasers (when last did you see one of those, huh? Huh!?).
Maybe the shiny bits seen on Mars are actually bits of silvery fish scales that had broken off. The total lack of silvery fish reported by Curiosity is evidence of the efficacy of these scales in hiding them in plain sight (scaly bastards, those Martian silvery fish).
Conceal or Reveal
'conceal them from predators, such as dolphin'
or if these new fish-fangled LEDs were to be used on bicycles...
'reveal then to predators, such as buses'
If any of you have ever driven (or cycled) along dark roads and come across a cyclist using powerful 'offroad lights' you'll have noticed that brighter, more efficient LEDs are sorely needed.
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