Tech + Engineering

28
Aug

Carbon-Nanotube Fuses Unleash a Surge of Electrons Called a Thermopower Wave

What happens when you coat yarn with explosives? You get a basic fuse suitable for fireworks. But what happens when you coat yarn made of carbon nanotubes with explosives? You get an entirely new way to create electricity.

In 2010, Michael Strano, a chemical engineer at MIT, and his lab were experimenting with strings made of carbon nanotube. After soaking one in TNT, they lit the end with a laser, and it burned like a fuse. But unlike a traditional fuse, a electrons surged ahead of the exothermic reaction, a phenomenon that Strano and his colleagues called a thermopower wave.

carbon-nanotube-illustration
The unique properties of carbon nanotubes help produce thermopower waves.

Those earliest experiments were nifty demonstrations, but little else. That may change soon, though. Kevin Bullis, reporting for Technology Review:

Now, Strano has figured out the underlying physics, which has helped his team improve efficiencies dramatically—by 10,000 times—and charted a path for continued rapid improvements. One day, generators that use the phenomenon could make portable electronics last longer, and make electric cars as convenient as conventional ones, both extending their range and allowing fast refueling in minutes.

At 0.1% efficient, Strano’s current carbon nanotube TNT strings are still a long way off from replacing conventional internal combustion engines that extend the range of hybrids—those are around 35% efficient. But a thermopower wave device would have several advantages. For one, it doesn’t have any moving parts, potentially making operation and maintenance simpler. Plus, they could be built much smaller than internal combustion engines, making them available to a wider range of devices.

Strano’s group has proven the concept using a number of different fuels, not just TNT. Here’s Nikki Gordon-Bloomfield, reporting for Transport Evolved:

So far, the team has launched thermowaves using ethanol, sugar and formic acid (from fire ants). The specific energy density of the process depends greatly on the fuel being used but, say the researchers, the process has the capacity to be many many times more energy dense than even the latest lithium-ion battery technology.

The lab’s next step is to boost the efficiency even further, and for that they’re looking at single-atom thick materials like graphene.

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