Invisibility Cloaks in the Real World

Invisibility cloaks are no longer found only in the imaginary worlds of James Bond and Harry Potter. In fact, various forms of invisibility cloaks have been around for quite a while.

Invisibility cloaks in science

A rigid hollow cylinder embedded in a homogeneous three-dimensional pentamode-metamaterial environment (white) is covered by a compliant pentamode-metamaterial shell (red). Any object can be placed inside of the hollow interior and thereby becomes ‘unfeelable’.

Science is the new magic

One example is an acoustic invisibility cloak that was created by Duke University in March. This omni-directional acoustic cloak is hidden from sound waves coming at it from any direction.

Researchers at Northwestern University made an invisibility cloak out of mirrors that can make an object appear to stop in time. If a pendulum swinging back and forth was cloaked, the pendulum would appear to be still and frozen in time while the actual pendulum continued to move.

Invisibility cloaks in action

There have been cloaks that hide objects from visible light and shield objects from microwaves and some forms of radiation. Researchers in Germany created an invisibility cloak that can actually shield an object from being felt. This mechanical invisibility cloak, made by the Karlsruhe Institute of Technology (KIT) in Germany, is unique. Like some light spectrum cloaks, it is made from a metamaterial, which is a specially made material that has properties not found in nature. However, this metamaterial is not used to bend light but redirect physical force. It is created by a 3D laser lithography machine that arranges the polymer material into needle-shaped cones in a crystalline lattice. This results in a structure around a semi-circle that cannot be felt by a finger or some more accurate measuring devices. The research paper refers to it as an “elasto-mechanical unfeelability cloak made of pentamode metamaterials”.

While a large scale commercially available light bending invisibility cloak is far from a reality due to the highly complex nature of bending thousands upon millions of wavelengths of photons around a large scale object flawlessly, the commercial availability for a material that can shield physical forces is much more probable. Currently there is not yet a commercial application set for this mechanical metamaterial, but it has a promising future.

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