Televisions and phones you can roll up and carry around are a step closer to reality.

Dutch scientists have discovered a type of graphene bubble that can change colour as it expands and contracts.

These 'mechanical pixels' could form the basis of screens of the future, which would be more flexible, durable and energy efficient than current LED technology.

The discovery was made by researchers from Delft University of Technology in the Netherlands.


Graphene is an ultra-thin layer of carbon just a one atom thick which has promised to revolutionise a number of fields, from engineering and medicine to commercial manufacturing.

The material is 200 times stronger than steel, and a sheet as thin as cling-film could hold the weight of a full-sized elephant.

The researchers say that, since their initial discovery of the pixels, they have now developed a technique to accurately control their colour changes.

They claim that they are now working on prototypes, and hope to have a screen ready to show off at the Mobile World Congress conference in March 2017.

The researchers made the discovery by setting up silicon panels layered with two thin sheets of graphene.

The silicon panels are pitted with small holes around ten times the width of a human hair, which the graphene layer stretches across like the skin of a drum.

When putting pressure through these cavities, the scientists noticed that the resulting bubbles of graphene changed colour with their size.

As the pressure inside the silicon deviated, the bubbles became concave or convex, shifting how light refracted through the graphene and triggering a series of colour changes.


'Graphene in principle is transparent; it's so thin that light doesn't get reflected,' PhD student and co-researcher Santiago Cartamil-Bueno told The Verge.

'But we were using a double layer of graphene, and that reflects more.'

How much or little the graphene bubble is inflated shifts the distance light has to travel through the silicon cavity.

This changes which part of the light spectrum is eventually absorbed and reflected back, warping the colour of the bubbles.

'Depending on the depth of the cavity you have different interference, and from this you get different colors of light,' says Mr Cartamil-Bueno.

Screens developed with this technology would be energy efficient, as once an image has been 'set' using the pixels no additional energy is required to maintain it.

Unfortunately, displays made using the pixels would not be visible in a dark room, as the way they are made makes back-lighting almost impossible.

The screen would be best viewed in direct sunlight.

The researchers caution that the technology is still in its early stages, and whether the graphene bubbles can be scaled up for mass production is yet to be seen.

The team face several challenges: colour changes have only been observed under a microscope so far, as the technology is very expensive to produce large-scale.

Hundreds of thousands of pixels would be needed to create even a tiny image, and the graphene bubbles can't be made too large or they would burst from the pressure.

The researchers are also yet to cultivate pure colours from the bubbles.

'I have seen the whole rainbow of colours, it's quite a natural effect,' says Mr Cartamil-Bueno.

'But you cannot get clean colours like pure red or pure blue.'

The next step for the researchers is to find a way to accurately control the pressure changes that warp the bubbles' colour.

The researchers have developed a technique for this electrostatic control, but their work in this area has yet to be peer reviewed.

What is graphene

Graphene is a single atomic layer of carbon atoms bound in a hexagonal network.

It not only promises to revolutionize semiconductor, sensor, and display technology, but could also lead to breakthroughs in fundamental quantum physics research.

It is often depicted as an atomic-scale chicken wire made of carbon atoms and their bonds.

Scientists believe it could one day be used to make transparent conducting materials, biomedical sensors and even extremely light, yet strong, aircraft of the future.

Similar to another important nanomaterial - carbon nanotubes - graphene is incredibly strong: around 200 times stronger than structural steel.