Tag Archives: metamaterial

BigBang

Using An Antimagnet to Build an Invisibility Cloak

The invisibility cloak of science fiction takes another step further into science fact this week. Researchers over at Physics arVix report a practical method for building a device that repels electromagnetic waves. Alvaro Sanchez and colleagues at Spain’s Universitat Autonoma de Barcelona describe the design of a such a device utilizing the bizarre properties of metamaterials.

[div class=attrib]From Technology Review:[end-div]

A metamaterial is a bizarre substance with properties that physicists can fine tune as they wish. Tuned in a certain way, a metamaterial can make light perform all kinds of gymnastics, steering it round objects to make them seem invisible.

This phenomenon, known as cloaking, is set to revolutionise various areas of electromagnetic science.

But metamaterials can do more. One idea is that as well as electromagnetic fields, metamaterials ought to be able to manipulate plain old magnetic fields too. After all, a static magnetic field is merely an electromagnetic wave with a frequency of zero.

So creating a magnetic invisibility cloak isn’t such a crazy idea.

Today, Alvaro Sanchez and friends at Universitat Autonoma de Barcelona in Spain reveal the design of a cloak that can do just this.

The basic ingredients are two materials; one with a permeability that is smaller than 1 in one direction and one with a permeability greater than one in a perpendicular direction.

Materials with these permeabilities are easy to find. Superconductors have a permeability of 0 and ordinary ferromagnets have a permeability greater than 1.

The difficulty is creating a material with both these properties at the same time. Sanchez and co solve the problem with a design consisting of ferromagnetic shells coated with a superconducting layer.

The result is a device that can completely shield the outside world from a magnet inside it.

[div class=attrib]More from theSource here.[end-div]

BigBang

Invisibility Becomes More than Just a Fantasy

[div class=attrib]From Discover:[end-div]

Two years ago a team of engineers amazed the world (Harry Potter fans in particular) by developing the technology needed to make an invisibility cloak. Now researchers are creating laboratory-engineered wonder materials that can conceal objects from almost anything that travels as a wave. That includes light and sound and—at the subatomic level—matter itself. And lest you think that cloaking applies only to the intangible world, 2008 even brought a plan for using cloaking techniques to protect shorelines from giant incoming waves.

Engineer Xiang Zhang, whose University of California at Berkeley lab is behind much of this work, says, “We can design materials that have properties that never exist in nature.”

These engineered substances, known as metamaterials, get their unusual properties from their size and shape, not their chemistry. Because of the way they are composed, they can shuffle waves—be they of light, sound, or water—away from an object. To cloak something, concentric rings of the metamaterial are placed around the object to be concealed. Tiny structures—like loops or cylinders—within the rings divert the incoming waves around the object, preventing both reflection and absorption. The waves meet up again on the other side, appearing just as they would if nothing were there.

The first invisibility cloak, designed by engineers at Duke University and Imperial College London, worked for only a narrow band of microwaves. Xiang and his colleagues created metamaterials that can bend visible light backward—a much greater challenge because visible light waves are so small, under 700 nanometers wide. That meant the engineers had to devise cloaking components only tens of nanometers apart.

[div class=attrib]More from theSource here.[end-div]