The July 2022 issue of IEEE Spectrum is here!

Close bar

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.

Keep Reading ↓Show less

This article is for IEEE members only. Join IEEE to access our full archive.

Join the world’s largest professional organization devoted to engineering and applied sciences and get access to all of Spectrum’s articles, podcasts, and special reports. Learn more →

If you're already an IEEE member, please sign in to continue reading.

Membership includes:

  • Get unlimited access to IEEE Spectrum content
  • Follow your favorite topics to create a personalized feed of IEEE Spectrum content
  • Save Spectrum articles to read later
  • Network with other technology professionals
  • Establish a professional profile
  • Create a group to share and collaborate on projects
  • Discover IEEE events and activities
  • Join and participate in discussions

3 Ways 3D Chip Tech Is Upending Computing

AMD, Graphcore, and Intel show why the industry’s leading edge is going vertical

8 min read
A stack of 3 images.  One of a chip, another is a group of chips and a single grey chip.
Intel; Graphcore; AMD

A crop of high-performance processors is showing that the new direction for continuing Moore’s Law is all about up. Each generation of processor needs to perform better than the last, and, at its most basic, that means integrating more logic onto the silicon. But there are two problems: One is that our ability to shrink transistors and the logic and memory blocks they make up is slowing down. The other is that chips have reached their size limits. Photolithography tools can pattern only an area of about 850 square millimeters, which is about the size of a top-of-the-line Nvidia GPU.

For a few years now, developers of systems-on-chips have begun to break up their ever-larger designs into smaller chiplets and link them together inside the same package to effectively increase the silicon area, among other advantages. In CPUs, these links have mostly been so-called 2.5D, where the chiplets are set beside each other and connected using short, dense interconnects. Momentum for this type of integration will likely only grow now that most of the major manufacturers have agreed on a 2.5D chiplet-to-chiplet communications standard.

Keep Reading ↓Show less