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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The Ultimate Transistor Timeline

The transistor’s amazing evolution from point contacts to quantum tunnels

1 min read
A chart showing the timeline of when a transistor was invented and when it was commercialized.

Even as the initial sales receipts for the first transistors to hit the market were being tallied up in 1948, the next generation of transistors had already been invented (see “The First Transistor and How it Worked.”) Since then, engineers have reinvented the transistor over and over again, raiding condensed-matter physics for anything that might offer even the possibility of turning a small signal into a larger one.

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