Blacker than Black
Deep in a cave you turn off your light and it is blacker than any night. You turn on your flashlight and the environment seems to suck the light out of it. That is the kind of black that scientists have recently created: a material that absorbs 99% of the light that strikes it.
Blacker than Black?
We call it this because it is mysterious, it is useful, and it is useful for stealth. Theaters frequently paint the stage area black as this eliminates any distraction from light that remains focused on the action. There is also a class of solar thermal panels that allow the sun to shine on a target area. That target is usually painted black but this only allows absorption of about 85% of the sun’s light. Using these metamaterials that are darker than black, efficiency can be significantly increased. There is also a military term for operations that are “off the books;” where stealth is paramount. Have you noticed what color the military paints stealth planes?
The Science
In a measure of self restraint, the scientific announcements refer to this technology as “darker than black”. Evgenii Narimanov at Purdue University created this hyperbolic metamaterial by growing silver nanowires in a membrane of aluminium oxide. Physorg.com provides us with the scientists explanation:
…the metamaterial’s very low reflectivity results from one of its hyperbolic properties: an infinite density of photonic states. This “super singularity” greatly increases the amount of light scattering from surface defects and corrugations in the metamaterial. The defects and corrugations scatter light primarily inside the material, basically “sucking” photons inside the hyperbolic medium.
Source: ‘Darker Than Black’ Metamaterial Promises Better Solar Cells via PhysOrg.com/Cornell University
Photo Credit via ‘Darker Than Black’ Metamaterial Promises Better Solar Cells’
For additional research: elsevier.com
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