Battery technology has come a long way since its inception, but the metals used in them are still difficult to dispose of or recycle. MIT is developing a solution to this problem by burning sugar on carbon nanotube wires. These nanotubes actually generate energy instead of just storing it. Since they're made from carbon and glucose, they're much more environmentally friendly than Lithium or Nickle based batteries.
This new application for carbon nanotubes is an extension of a discovery made in 2010, also made by MIT. Researchers discovered that carbon nanotubes coated with reactive fuel produced heat while decomposing. When the fuel was ignited at one end of the nanotube, the heat produced a thermal wave that traveled through the nanotubes in a loop. This heat traveled around the tube at speeds 10,000 times faster than a normal chemical reaction (In this case combustion) and had a temperature of 3,000 Kelvins. The most important, yet unexpected discovery was that this heat loop created an electrical current. In the original paper, the nanotubes were said to be 100 times more efficient than lithium ion batteries. In the 5 years since then, MIT says that they've improved on that design to make it more than 10,000 times more efficient.
A model of a carbon nanotube
The technology is still a few years out from being commercially viable, and there is a lot of potential for improvement. Sucrose was used originally because of its availability and chemically stable properties. By using different fuel sources, MIT's team thinks that they can make these nanotubes generate even more power. This will require a lot more testing to ensure safety as they experiment with more volatile compounds for fuel.
“I believe that we are still far from the upper limit that the thermopower wave devices can potentially reach..However, this step makes the technology more attractive for real applications.” -Dr. Kourosh Kalantar-Zadeh, RMIT University, Australia
These real-world applications are the most exciting part about all of this. These nanotubes have two important properties that separate them from the batteries and generators of today. The first being that these nanotubes are tiny, only a few nanometers thick, and the walls are comprised of individual carbon molecules. This will allow designers to make reliable power supplies for microscopic devices. The second benefit is their long shelf-life. The nanotube power sources can be stored for years before being activated.
The potential applications for carbon nanotube power sources are especially intriguing in the medical and aerospace fields. Their small size and non-toxic degradation make them especially viable for use in medical implants and internal diagnostic sensors. These could be the key to finally making those nano-robots that flow through people's blood in comic books. They could also be a major breakthrough for space exploration. Since these power supplies have to be ignited before they generate power, they're ideal for space probes being sent to the ends of the solar system and beyond.
The most exciting inventions that will stem from carbon nanotube power sources will most likely be the ones that nobody has thought of yet. That's often how things go in science and engineering, and after all, the tubes' electrical conductivity was an unexpected discovery.