Materials

Nanoparticles turn a clear window into a mirror and back again

Nanoparticles turn a clear win...
For the first time scientists have created a material that can switch back and forth between transparent and reflective
For the first time scientists have created a material that can switch back and forth between transparent and reflective
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For the first time scientists have created a material that can switch back and forth between transparent and reflective
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For the first time scientists have created a material that can switch back and forth between transparent and reflective
Before current is applied
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Before current is applied
After current is applied. Note the coin's reflection appearing
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After current is applied. Note the coin's reflection appearing
The device is still experimental but the theory and proof of concept is successful paving the way for tunable materials in the future
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The device is still experimental but the theory and proof of concept is successful paving the way for tunable materials in the future

Creating a material that can alter its optical properties in real time has proved challenging for scientists, but a team at Imperial College London has finally achieved a major breakthrough by developing a material that can transition from clear to reflective and back again using an array of gold nanoparticles.

As well as overcoming the difficulty in creating a tunable material on such a tiny scale, the big innovation here was using electrical currents as the trigger for the shift in optical properties. Previous nanoscopic systems have successfully altered optical properties through chemical processes, but this was not reversible.

The team utilized an array of gold nanoparticles, localized between two different liquids. The density of the nanoparticle layer could then be modulated by applying a small electrical voltage. This either made the nanoparticles cluster together densely and create a reflective mirror, or separate apart enough to allow light to pass through and make the material transparent.

Before current is applied
Before current is applied

"It's a really fine balance – for a long time we could only get the nanoparticles to clump together when they assembled, rather than being accurately spaced out," says co-author of the study, Professor Joshua Edel. "But many models and experiments have brought us to the point where we can create a truly tuneable layer."

After current is applied. Note the coin's reflection appearing
After current is applied. Note the coin's reflection appearing

The novel reversibility of the process allows for, not only a future of funky alternating mirror-windows in your house, but an assortment of practical applications, including tunable optical filters for telescopes or chemical sensors.

Take a look at the material switch from transparent to reflective in the video below.

The research was published in the journal Nature Materials.

Source: Imperial College London

Electrotuneable Nanoplasmonic Liquid Mirror

1 comment
LesBorean
Can this transition be tuned to in-between states where the material is partially transparent while partially reflective?