Published by the Students of Johns Hopkins since 1896
September 19, 2020

Scientists invent cloak of invisibility

August 3, 2011

I’ll admit to being one of the die-hard lunatics at the Harry Potter and the Deathly Hallows premiere, covered in wizard savvy accessories including an upside-down wooden spoon doubling as a wand. With all of the quizzical stares I endured that night, I could have seriously used Harry’s invisibility cloak.

Nano Letters

This cloak is the first of its kind to operate successfully at frequencies detectable by the human eye. Similarly constructed cloaks known as metamaterial cloaks, or cloaks made using artificial materials with manipulated properties, have been invented in the past. So far, all have had a limited range of concealment. For instance, a cloak constructed in 2006 hid objects only in the microwave region of the electromagnetic spectrum.

The new metamaterial cloak can conceal a 0.000024 by 0.000012 inch object, a size roughly equivalent to the diameter of the nucleus in a eukaryotic cell. Alternatively, that is one-hundredth of a human hair.

Constructed from silicon oxide lined with silicon nitride, the cloak contains miniscule concentric holes in a specially designed pattern. The holes act on light by altering its speed and making it as though the light never even hit the object.  Thus, the light passes through the holes undetected.

The cloak can act on light of any given wavelength in the visible spectrum, no matter the angle at which it approaches the cloak. The combination of these qualities is a huge step forward in invisibility technology.

Scientists are working on developing techniques to reduce the time involved in the cloak’s assembly and are speculating that a larger cloak is likely feasible in the future.

—Mali Wiederkehr, Science & Technology Editor

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