Stretchable Tunable Oscillators: Metamaterials Get A Shot In The Arm!

Metamaterials are the materials designed using nanotechnology. They are designed to exhibit some astounding properties which are not seen naturally.  Materials with negative refractive indices are focused primarily. The applications and the end products of this technology are awesome. There have been products which could be built only with the application of metamaterial technology. These include invisibility cloaks, microscope lenses with an ultra high resolution and special coatings for solar cells which can absorb a high amount of incident radiation. What makes metamaterials to have their share of limelight? The materials are designed of such a composition that they can interfere with the electromagnetic waves. These include not only the visible light but also the microwaves and a myriad range of spectrum.

#-Link-Snipped-#What made the metamaterials impractical was their operation in small array of wavelength of the light wave.  The researchers at California Institute of Technology (Caltech) led by Harry Atwater, have developed a new technology which promises to remove this drawback in the metamaterials. The researchers have experimentally demonstrated the same by building a metamaterial consisting of an array of resonators on a stretchable polymer film. The oscillators consist of two parts: C and I shaped materials. Each block of the oscillator has one C and I placed next to each other with a distance of 50 nanometers separating them. By changing the distance between the ‘C’s and ‘I’s, the wavelength of light for which the oscillator will oscillate can be decided.

Harry Atwater, professor of applied physics and materials science demonstrated that the wavelength at which the materials resonate can be changed in wide limits by just changing the distance between two parts of the components. This could be achieved by stretching the polymer sheet to more than half of the original size. What is more interesting that even when the sheet was stretched, there was no negative effect on the dimensions of the component of the oscillator: C’s and I’s. The wavelengths could be varied in a broad range of infrared spectrum.

The metamaterials in past were tuned by techniques which consumed more power and even then the range of wavelengths over which the material could be made to resonate was limited. Some of the methods to tune the materials include application of voltage and barrage of laser light on the material. But this novel method is both energy efficient and provides huge flexibility. The metamaterials which are tuned in infrared spectrum are designed in a manner of circuit boards. This makes it easier to tune with the help of small bursts of power. But the use of stretchable design will also allow the use of active materials in this range of light.

The experimental demonstration was done at Caltech by designing a chemical sensor. The chemical sensor was designed to detect a type of carbon-hydrogen bond. The bond has an associated wavelength with it due which it can be identified in a given sample. The oscillators were designed in a flexible array and their sensitivity was tested. The oscillators were subjected to different strains and it was concluded that their sensitivity could be improved by just stretching the polymer sheet. This could result in a single sensor which could be used for the detection of multiple chemicals.

Future applications include thermal photovoltaic cells that can adapt to weather and have a constant efficiency. Or imagine having glares which could automatically change their properties according to the sunlight. The invention and the successful demonstration of the technology have given birth to newer possibilities which couldn’t even be thought of in the past.

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