Stick-on screens open up a new vista for window projections

Scientists have created a transparent screen that can turn any window into a display for moving images.

The screens, which are made by adding tiny nanoparticles that reflect blue light into a liquid polymer, can be stuck on to any window.

The nanoparticles are invisible to humans, creating the transparency, but images projected in blue light show up.

The team asserts in the journal Nature Communications that it is simpler to make than existing similar screens.

Stick-on screens could be used to host advertisements on shop windows or for office presentations.

Pour it on

Transparent screens themselves are not new; from Google glass to Minority Report-style computer screens, there are many now in commercial development.

But while these employ complicated, expensive technology - a head-up display projected onto a tiny prism embedded in Google glass, or LEDs actually embedded within transparent computer screens - this new method is very simple.

"We literally just pour the nanoparticles into the polymer before it solidifies," explained lead researcher Chia Wei Hsu, a graduate student from MIT and Harvard University, US.

Only a few thousandths of a gram of nanoparticles are needed per square centimetre of screen, meaning the technology is also relatively cheap.

'So simple'

In the case of this latest development, since each type of particle reflects only one colour, the screens display just one colour of image.

The researchers say it would be possible to have multiple colours, but the more nanoparticles that are added to the screen, the more opaque it would become.

"Since it's so simple to deploy, you could paste this [plastic] sheet onto any surface," Mr Hsu told BBC News.

"You could put it on store front windows for advertisements or information about what's inside the store, or we could use it for office windows, so you could then have your presentation [shown] on the window of your office."