Researchers from Amsterdam have discovered a material that can be used to transport ultra-thin (2D) materials. And there’s a good chance you’ll find it right in your kitchen cupboard.

In the case of materials just one atom thick, the height is negligible. 2D materials are therefore referred to as ‘flat’ materials. They often possess remarkable properties, such as extremely high electrical conductivity, a strong interaction with light or a remarkable combination of strength and flexibility. The best-known 2D material is probably graphene, the 2D form of graphite. This is because, in 2010, two physicists won the Nobel Prize for their method of ‘harvesting’ graphene from graphite – namely, by simply peeling it off with a piece of sticky tape.

Since that discovery, the methods for producing 2D materials and incorporating them into devices or instruments have certainly been refined, but have not changed fundamentally. The process still involves pressing an adhesive tape onto a crystal and then peeling it off again. Since 2018, a gold film has often been used instead of adhesive tape to peel the 2D material off the crystal. The advantage of this is that there is less flaking, resulting in larger, intact sheets.

Cling film

The next challenge is to transfer the material onto another surface without damaging it. This is because the atom-thick material can be damaged by even the tiniest imperfection.

Scientists from the University of Amsterdam (UvA), the Advanced Research Centre for Nanolithography (ARCNL) and the NWO institute AMOLF are now presenting a material onto which 2D material can be transferred more effectively than was previously possible, as they report this month in the scientific journal ACS Nano. The material in question is cling film – the thin plastic on a roll found in many kitchen drawers and used to wrap up leftovers before they go into the fridge.

Scanning-elektronenmicroscoopafbeelding van een schilfer 2D-materiaal op een puntig oppervlak. Bron: Universiteit van Amsterdam

European

‘Cling film turned out to have exactly the right properties for handling the delicate 2D materials gently and effectively,’ says Bernardo Dias, a PhD student at the University of Amsterdam (UvA) and lead author of the scientific article on this subject, in a UvA press release. However, it must be European cling film, the researchers note – the Japanese variety, at any rate, does not work as well.

‘We tried to replicate the results of a research group in Japan, but it turned out that cling film in Europe is made from a different polymer,’ says Jorik van de Groep, head of the 2D Nanophotonics Group at the UvA Institute of Physics, in the same press release. ‘The polymer we use here melts at 120 degrees Celsius, whereas theirs did not. That property turned out to be the decisive factor for a successful 2D material transfer: we were simply able to melt our cling film onto the material to make it adhere.’

Applications

Improved transfer of 2D materials without them disintegrating into fragments brings applications for these materials a step closer. Examples include the manufacture of transistors based on 2D materials or the development of ultra-thin optical elements such as lenses and modulators. It is also possible to stack different 2D sheets on top of one another, like a kind of lasagne, to form a new material, which may in turn possess different properties.

Opening image: Depositphotos