Passengers waiting at a bus station using smart phones

Ultra-thin heat insulation could contribute to the manufacture of smaller versions of electronic devices such as mobile phones. Credit: Woohae Cho/Bloomberg/Getty

Applied physics

How to make a stout yet skinny heat shield

Promising thermal-insulator materials are tens of thousands of times thinner than a human hair.

Scientists have made highly effective thermal insulators from materials just a few atoms thick.

Two-dimensional materials such as graphene consist of a single layer of atoms. By stacking sheets of 2D materials on top of one another, researchers can create structures with notable electronic and optical properties, such as superconductivity.

Eric Pop at Stanford University in California and his colleagues applied this stacking technique to achieve remarkable thermal effects. The researchers piled up 2D sheets of up to four compounds — graphene, molybdenum diselenide, molybdenum disulfide and tungsten diselenide — to make thermal insulators less than 3 nanometres thick.

The team found that such stacks block heat more than 100 times better than does glass, which is itself considered to be a good thermal insulator. The mixed atomic layers stop heat from spreading by preventing quantum units of heat, called phonons, from travelling between layers.

These layered 2D materials could help to protect electronic devices from heat and prevent excess heat from such devices affecting their surroundings. The 2D stacks could also be used to channel heat similarly to the way electrical insulators are used to route electricity in circuits.