Nanomaterial magic: from a window to a mirror with the flick of a switch | Science

Nanomaterial magic: from a window to a mirror with the flick of a switch | Science

Australian scientists have developed a technique to create temperature-controlled nanomaterial that could be used to turn a window into a mirror at the push of a button.

The method, developed by a team of 12 at the Australian National University, could be used to protect multibillion-dollar satellites from harmful radiation, create energy-efficient temperature-controlled homes, or just for the trivial delight of switching a mirror on and off, said the lead researcher, Dr Mohsen Rahmani.

The breakthrough is the result of two years of work from Rahmani and his team, who experimented with nanoparticles of different materials to see how they responded to light and heat.

They found that a film made of certain combinations of nanoparticles could be “tuned” to change from a frequency that transmits light or radiation to one that reflects.

“The most important and newest thing in this research work we have done is [figure out] that they are tunable,” he told Guardian Australia. “You have control on their optical properties and you can make them transmit the light or reflect the light or something in between.

“If I want to just explain in plain English: because the dimensions of them are comparable with the wavelengths of the light at different frequencies, designed for different frequencies, they can interact with light and they can redirect the trajectory of light, transmit or reflect it. Because the dimensions are in the same order as the light.”

The trigger is temperature. Because nanoparticles are so small â€" more than 500 could fit on the tip of a human hair, Rahmani said â€" they can be distributed across a surface like glass in such a way that they reflect off all light, or just half of the light, depending on the temperature.

“That’s why it’s great for the energy savings because you can adjust them to have 50% transmission and 50% reflection, or 100% transmission and 0% reflection,” Rahmani said. “So you can adjust them from zero to one, whatever you want, from reflection to transmission.”

The switch would just be localised temperature control, similar to the demister in a car.

“You can use the same mechanism by locally heating those nanoparticles,” he said.

The technology has the potential to be particularly lucrative in the telecommunications industry, which could use a thin, almost weightless layer of nanomaterial to replace lenses, mirrors and other bulky apparatus designed to protect satellites from harmful radiation.

Nanomaterial is already used in the space industry. Where ANU’s discovery differs is the ability to change the function of the nanomaterial without making any physical change to the material.

“So far when you want to change the function you had to change the component itself physically, but now you don’t need to change the component any more and you just need to adjust it and control the temperature as you wish,” Rahmani said.

“These nano layers are so small, so light, you can just accommodate them on any small and micro satellite and cover them from the harmful radiation … [And] if you want to change the frequency you just need to change the materials because different materials have different optical properties.”

With adequate investment and the right people, Rahmani said, the technology could be on the market, for industrial purposes or just for consumers who want to switch their car windows to a mirror because it looks cool, within a few years.

“We have the technology but we need some probably industrial partnership to make the industrial prototypes,” he said. “It’s not very far from our sight, really.”

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