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Dec 30th 2019

Engineered Metamaterials Make Invisibility Cloaks and More

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The most common materials in the world, including plastic, steel, glass or wood have distinct molecular and chemical properties that give them intrinsic qualities, such as strength, flexibility or transparency. But an entirely different class of materials, called metamaterials, are coming onto the scene.

Artificially engineered, these materials have unique geometries and physical structures that can manipulate any mechanical or electromagnetic wave that passes through them. Metamaterials can perform a host of futuristic tricks; they can absorb sound waves to produce silence, bend light to create an invisibility cloak and dampen seismic waves to safeguard a building against an earthquake.

Metamaterial applications are numerous, but here are five of the coolest.

Sound Silencers

If you’ve ever traveled by train or plane, you know the thunderous noise large engines can make. Industrial noise occurs in factories, too — it even emits from the fan in your refrigerator. Some scientists, like Yun Jing and his colleagues at North Carolina State University, are building metamaterials to quiet these large machines.

In the journal of the Annual Review of Materials Research, Jing describes a material he designed that behaves like a kind of sound cage. Gaps in the cage are large enough to allow air to pass through but small enough that sound waves become trapped inside. Soundproof and ventilated, the cage could keep engine noise to a minimum.

Sonar Deflectors

In the deep ocean, submarines crews use sound waves, or sonar, to detect other seafaring vessels. But what if you have a stealth mission ahead of you and you don’t want to be detected? Talk to engineer Amanda Hanford and her team at Pennsylvania State University. They designed a metamaterial device that renders objects invisible to sound. If the hull of a submarine were covered in this material, it would force the energy from oncoming sound waves to spread around the object, instead of bouncing off and returning a signal, reports the BBC.

Earthquake Dampeners

Earthquakes have injured or killed hundreds of thousands of people around the world since 2000, reports Our World in Data, and the annual damage earthquakes cause to infrastructure is in the billions of dollars. Researchers are looking at various applications of metamaterials to soften the blow of these violently shaking natural disasters.

One method involves building blocks called robotic meta-atoms, developed by a group of physicists from the University of Amsterdam, says PhysOrg. Each tiny device vibrates on a unique spring, causing the concentric rippling energy passing over it to shift and move in only one direction. That dissipates the wave in one direction and amplifies it in another. A device made from these meta-atoms could potentially redirect the energy of a seismic wave away from a building and in a safer direction.

Heat Shields

Dozens of space companies and agencies are currently drafting plans to send satellites and spaceships into orbit and beyond. Once outside Earth’s protective atmosphere, spacecraft electronics become vulnerable to infrared heat and radiation from the sun. Current methods to protect them involve radiator panels made from quartz tiles. But these tiles are heavy, adding to the cost of launches.

Last year, researchers from the University of Southampton announced they had developed a thin, lightweight coating from metamaterials designed to radiate infrared heat away from spacecraft. Called a metamaterial optical solar reflector, or a meta-OSR, the material is made from metal oxide, a material commonly used for transparent electrical contacts. The team created a pattern in the surface of the material to bend each electromagnetic wave in the infrared spectrum away from it and also reflect sunlight.

Invisibility Cloaks

Scientists are closer than ever to creating an invisibility cloak that competes with Harry Potter’s.

In research published last year in the journal Optica, researches led by engineer José Azaña reported that they had developed a spectral cloaking device that could make objects invisible in daylight. The device, called an optical filter, manipulates the various frequencies of visible light, such as the red, blue and green wavelengths of light seen in a rainbow.

The filter works by shifting one frequency of light to another as the light passes through the object, reports Tech Times. Once the light wave has passed, it returns to its original state. For instance, the filter would shift the red wavelength of light passing over a red apple to another frequency, rendering the apple invisible. Such a filter could be used to cloak military operations, but it could also be used in the telecommunications industries to improve radio signals.

Each year, scientists improve upon the technology of metamaterials, remarkably engineered coatings, devices and components. These structures, which are typically microscopic or smaller, allow scientists to control mechanical and electromagnetic waves in novel and surprising ways. From saving lives to shielding covert operations from enemy eyes, these materials push the limits of light and sound and will take humans into a future we haven’t yet imagined.

Check out Northrop Grumman career opportunities to see how you can participate in this fascinating time of discovery in science, technology, and engineering.

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