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Disappear into thin air? Scientists take step toward invisibility.

By Peter N. SpottsStaff writer of The Christian Science Monitor / October 20, 2006



Flip a switch and make something disappear? It's been the stuff of science fiction for decades. Now, two Duke University scientists and their colleagues have built the world's first device to render an object invisible.

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At least, it's invisible to microwaves.

But researchers say the work demonstrates that, in principle, objects could be made to disappear from radar, cameras, and other detection devices. The trick? A new class of engineered substances called metamaterials.

These materials could someday add muscle to microscopes, reduce the size and increase the capability of radar, sonar, and other remote-sensing devices, and cloak or shield objects, researchers add. The rudimentary microwave cloaking device was reported in Friday's edition of the electronic journal Science Express.

It's hard to overstate "how amazing this whole field is," says Nathan Myhrvold, former chief technology officer for Microsoft Corp., who now heads Intellectual Ventures, a company in Bellevue, Wash., that focuses on inventions.

Metamaterials exhibit electrical and magnetic properties not found in natural materials. In essence, they respond to radiation – whether microwaves or visible light – in new ways. The US military's current stealth technology makes a plane hard to detect by radar. In theory, metamaterials could make it disappear.

The cloaking device, announced Friday, looks deceptively simple. "It's a compelling example of what we can do" with key properties that metamaterials exhibit, says David Smith, a Duke University professor of electrical and computer engineering who is one of the field's two founding fathers.

In essence, the device consists of tiny copper antennas etched on thin, nested cylinders of circuit-board material. In the center, the team put a small object that would send microwaves flying helter-skelter if they struck it. A microwave beam slipped past this array of antennas and the target it encircled, much like ocean swells flow past a small offshore rock poking through the surface. The microwaves slipped by the setup virtually unaffected.

Potential applications range from improving cellphone technology to shielding people and equipment from disruptive forms of radiation.

The field of metamaterials is still in its infancy, Dr. Smith says. In 1967, Russian physicist Victor Veselago showed that it was possible in principle for matter to appear to display oddball traits.

Light could appear to move backward. A reed would appear to bend back out of a batch of metamaterial, rather than continue in the same general direction, as it would in water. A lens made from this theoretical material would perfectly reproduce the tiniest details of the object behind it – at least over very short distances – in ways no traditional lens can.

In the late 1990s, physicist John Pendry of London's Imperial College began making metamaterials. By tailoring their designs, researchers could give these materials unique electrical and magnetic properties that their constituents – like the copper and fiberglass in Smith's device – couldn't hope to match individually.

In 2000, Smith found a combination of metamaterials that displayed the oddball optical properties Dr. Veselago's calculations predicted.

While Smith and his colleagues are working to cloak a three-dimensional object, others are looking to perfect superlenses.

In May, a team led by physicist Xiang Zhang of the University of California at Berkeley unveiled the first crude superlens using ultrahigh-frequency sound waves.

The hope, he says, is to develop devices, such as ultrasound imagers and sonar, that are smaller and lighter and render objects in far more detail than today's devices can.

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