Australasian Science: Australia's authority on science since 1938

Nanotubes Power Up

By Stephen Luntz

Nineteenth and 21st century technologies have come together with the discovery that carbon nanotubes dipped in nitrocellulose could form lightweight batteries capable of powering very small devices.

Nitrocellulose, also known as guncotton, is a highly explosive material. It was used in film reels until the 1950s, a fact responsible for several tragedies when film caught fire and incinerated an entire cinema. A/Prof Kourosh Kalantar-zadeh of RMIT’s School of Electrical and Computer Engineering was on sabbatical at Massachusetts Institute of Technology when he helped discover a new application.

“By coating a nanotube in nitrocellulose fuel and igniting one end, we set off a combustion wave along it and learned that a nanotube is an excellent conductor of heat from burning fuel. Even better, the combustion wave creates a strong electric current,” Kalantar-zadeh says.

Nitrocellulose nanotube batteries might have several advantages over current systems. For one thing, their nanoscale means they could provide a power source for tiny robots operating within the body to remove clots or fight cancer.

Kalantar-zadeh notes that batteries have not miniaturised as fast as the electronic components they power. Microscopic devices have been designed but the power supply “is as large as your watch battery”.

The nanotubes also release power much more rapidly than other stores of energy. This has advantages in applications such as car batteries, where large amounts of power are needed quickly to get the car started but sustained release is not necessary.

Furthermore they are light, storing far more energy per gram than alternatives. Combining these features, Kalantar-zadeh contemplates car batteries that weigh 10 grams rather than 20 kg.

The nanotubes can be reused, and Kalantar-zadeh even claims that “they become better with repeated application in solution”. However, the chemical reaction is not reversible so they cannot be recharged from a power point.

Moreover, the conversion to electricity is currently very inefficient, with “2–3% the highest ever reported” according to Kalantar-zadeh. Improving this efficiency is seen as the largest obstacle to practical application.