Atom-thin insulators pave the way to new, thinner devices

The heat given off by devices can certainly be annoying when you’re home, in bed, laptop on your belly, watching Youtube videos of cats to get you sleepy. But, it can also be dangerous for the devices themselves. Excess heat contributes to malfunctions and, in extreme cases, can even cause lithium batteries to explode.

In order to keep this heat contained in heat-generating components like microprocessors, designers and engineers use sheets of glass, plastic, or pockets of air as insulation. All of them, however, take up quite a lot of space.

And space is a commodity

In an effort to make insulation — and thus the devices themselves — as compact as possible, researchers at Stanford University have shown that a few layers of atomically thin materials, stacked atop hot spots, can provide the same insulation as a sheet of glass 100 times thicker.  According to Eric Pop, Professor of Electrical Engineering and senior author of the paper, this line of research will help make our devices even more compact than today.

“We’re looking at the heat in electronic devices in an entirely new way,” Pop said.

This paper is built on a simple but powerful shift in approach: the team treated heat as sound.

When you get down to it, heat, really, is sound. Heat is actually the vibration or movement of particles in a body — the more they vibrate, the hotter the object gets.

The heat in our devices is generated by electricity. As electrons move through wires, they collide with the metal atoms of said wires. Each collision causes an atom to vibrate, and the more current flows through the material, the more collisions occur. In the end, you are left with a number of atoms, all enthusiastically vibrating. Moving atoms is also what generates sound, but the electricity-induced vibrations move through the solid material at frequencies far above what our ears can pick up, so we can’t hear it — but we do feel that energy as heat.

This line of thinking inspired the team to borrow a few principles from audio insulators. Music recording studios, for example, are quiet thanks to thick glass windows that block the exterior sound — this is pretty similar to how we design heat insulators today. However, the obvious problem with this is that it relies on the sheer mass of material — and thus, on volume — to block heat.

So, instead, the team borrowed a trick from homeowners and installed multi-paned insulators. Just as a multi-paned window uses layers of air to insulate your room, so too does the team’s insulator.

“We adapted that idea by creating an insulator that used several layers of atomically thin materials instead of a thick mass of glass,” said postdoctoral scholar Sam Vaziri, the lead author on the paper.

The team used a layer of graphene and three other sheet-like materials — each three atoms thick — 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.

So far the technology is solid, but the team needs to find an effective means of mass-producing the atomic insulator in order to bring it to market.

“As engineers, we know quite a lot about how to control electricity, and we’re getting better with light, but we’re just starting to understand how to manipulate the high-frequency sound that manifests itself as heat at the atomic scale,” Pop said.

The paper “Ultrahigh thermal isolation across heterogeneously layered two-dimensional materials” has been published in the journal Science Advances.