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Three Weird Ways to Make Things Invisible

Objects can go undetected by sight, sound, or heat with these tricks

4 min read
Steven Cummer's cloaking pyramid.
Photo: Duke University

In 2006, scientists at Duke University captured the world’s imagination by announcing they had created an invisibility cloak. It could hide an object only from a particular wavelength in the microwave region, and only when viewed from certain directions, but it sparked waves of research along with countless cracks about boy wizards and Romulan warbirds. You still can’t hide a spaceship, but that hasn’t stopped scientists from coming up with new and strange ways to make small objects undetectable, and the past few months have produced particularly unusual innovations.

Invisibility is accomplished using metamaterials, which feature structures that are substantially smaller than the wavelengths of light. For instance, an early metamaterial, described in 2008 by Xiang Zhang, a professor of mechanical engineering at the University of California, Berkeley, consisted of 30-nanometer-thick layers of silver interwoven in a fishnet pattern with 50-nm-thick layers of magnesium fluoride. The right arrangement of structures gives the material a negative index of refraction, allowing it to bend light of a particular wavelength in directions it would not normally bend. With careful engineering, the idea goes, you could route the light around an object and let it continue on as if the object weren’t there.

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A Circuit to Boost Battery Life

Digital low-dropout voltage regulators will save time, money, and power

11 min read
Image of a battery held sideways by pliers on each side.
Edmon de Haro

YOU'VE PROBABLY PLAYED hundreds, maybe thousands, of videos on your smartphone. But have you ever thought about what happens when you press “play”?

The instant you touch that little triangle, many things happen at once. In microseconds, idle compute cores on your phone's processor spring to life. As they do so, their voltages and clock frequencies shoot up to ensure that the video decompresses and displays without delay. Meanwhile, other cores, running tasks in the background, throttle down. Charge surges into the active cores' millions of transistors and slows to a trickle in the newly idled ones.

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