Excess heat given off by smartphones, laptops, and other electronic devices contributes to malfunctions and, in extreme cases, can even cause lithium batteries to explode. To guard against issues, engineers often insert glass, plastic, or layers of air as insulation to prevent heat-generating components like microprocessors from causing damage.
Researchers have demonstrated that a few layers of atomically thin materials, stacked like sheets of paper on hot spots, can provide the same insulation as a sheet of glass 100 times thicker. In the near term, thinner heat shields will enable engineers to make electronic devices even more compact than those currently available.
Heat from smartphones or laptops is actually an inaudible form of high-frequency sound. Electricity flows through wires as a stream of electrons. As these electrons move, they collide with the atoms of the materials through which they pass. With each such collision, an electron causes an atom to vibrate; the more current flows, the more collisions occur, until electrons are beating on atoms like hammers on bells. These vibrations move through the solid material at frequencies far above the threshold of hearing, generating energy that is felt as heat.
Music recording studios are quiet thanks to thick glass windows that block the exterior sound. A similar principle applies to heat shields in electronics. Layers of air between sheets of glass with varying thickness make interiors warmer and quieter. The new insulator uses several layers of atomically thin materials instead of a thick mass of glass.
A layer of graphene and three other sheet-like materials — each three atoms thick — were used to create a four-layered insulator just 10 atoms deep. Despite its thinness, the insulator is effective because the atomic heat vibrations are dampened and lose much of their energy as they pass through each layer.
To make nanoscale heat shields practical, the researchers will have to find a technique to spray or otherwise deposit atom-thin layers of materials onto electronic components during manufacturing. They also hope to one day control the vibrational energy inside materials the way they now control electricity and light.