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Hyperlens sharpens sights with sound

A versatile, new hyperlens could soon give expecting parents high-definition baby pictures as well as provide ship captains incredibly accurate maps of the sea floor.
/ Source: Discovery Channel

A versatile, new hyperlens developed by scientists at the University of California, Berkeley could soon give expecting parents high-definition baby pictures as well as provide ship captains incredibly accurate maps of the sea floor.

"The images you get when you try to look at unborn babies (with ultrasound) are pretty fuzzy. You can see an arm, but you can't clearly see facial structures," said Xiang Zhang, co-author of a recent paper in the journal Nature Materials.

"With this new technology, we will be able to resolve a baby's face before it's born."

The brass hyperlens developed by Zhang is made of 36 fins, spread out in a half circle like a handheld fan. Each fin, roughly 20 centimeters (7.9 inches) long, compresses and magnifies incoming sound waves, making it easier to tease out the image of a tiny nose or the line of a check bone from an ultrasound.

Zhang made his hyperlens from brass for easier production. However, a hyperlens could be produced from many other more durable materials, including steel.

That strength will be important for another use as well. Deploying a hyperlens underwater could give submarines a detailed view of underwater geographical features or incoming enemy subs.

A hyperlens is part of a larger group of materials known as metamaterials. Unlike normal materials, which derive their physical properties from their chemical components, metamaterials derive their physical properties from their physical structure.

These structures need to be much smaller than the wavelength they intend to manipulate. Scientists from all over the world have relentlessly created ever-smaller structures to manipulate ever shorter wavelenghts of light. This includes light waves short enough to be seen by the human eye, creating the so-called "invisibility cloak."

Metamaterials can now manipulate an entirely different kind of wave. Unlike an electromagnetic wave, which doesn't need a medium to propagate through, sound waves need some physical material such as air or water.

"These are really different phenomena," said Viktor Podolskiy, a physics professor at Oregon State University studying metamaterials. "But the equations that govern both their actions are very similar."

This new metamaterial is the first acoustic hyperlens Podolskiy has heard of. Scaling up its production for commercial use instead of laboratory experiments will likely take years, says Podolskiy. Metamaterials can already be found in several commercial devices, including wireless routers and a new cell phone from LG.

"This is not just an improvement in fabrication technique," said Zhang. "This is a new physics that enables us to design physical properties that don't normally exist in nature."