Sumio Iijima, Akira Koshio & Masako Yudasaka

Winners of the European Inventor Award 2015 in the category Non-European countries

Imagine carbon atoms, each joined to three neighbouring atoms, in a hexagonal or honeycomb pattern to form a sheet just one atom thick. Now imagine that sheet rolled so that the edges join to form a cylinder – a carbon nanotube. These tubes might be singular (so-called single-walled) or comprise two or more concentric tubes of different diameters – one inside another (so-called multi-walled). Carbon nanotubes may have diameters of just a few nanometres but lengths that can reach several millimetres – like minute bits of string.

Although award-winning physicist Sumio Iijima might modestly credit his discovery of multi- and single-walled carbon nanotubes to good fortune, their unearthing was much more the culmination of years of research and hard work than pure luck. From developing a specialized high-resolution electron microscope, while still an undergraduate student, to years spent researching atomic structures of materials such as carbon, Iijima was in a unique position to make one the biggest discoveries in material sciences over the last few decades.

Societal benefit

Iijima’s discovery shook the foundations of his field. Until he identified nanotubes, pure carbon was believed to only exist in three forms: diamonds, graphite and the hollow, ball-shaped fullerenes. The identification of carbon nanotubes sparked newfound attention in Iijima’s field and since then, a myriad of uses have been found for these super-thin yet highly conductive molecules.

Carbon nanotubes have formerly unknown electrical and thermal properties. They are much more conductive than copper, and they have found a variety of chemical, mechanical and optical applications. Many materials, including polymers and metals, can be significantly improved by using carbon nanotubes as filler: They render solar panels more effective and automotive and airplane parts more robust, for example.

Economic benefit

The commercialisation and market introduction of carbon nanotubes is in full swing, but currently limited to the use of bulk nanotubes – that is to say, a mass of unorganised nanotubes used as composite fibres in polymers to bolster their mechanical, thermal and electrical properties.

Carbon nanotubes have formerly unknown electrical and thermal properties. They are much more conductive than copper, and they have found a variety of chemical, mechanical and optical applications. Many materials, including polymers and metals, can be significantly improved by using carbon nanotubes as filler: They render solar panels more effective and automotive and airplane parts more robust, for example.

How it works

Although carbon nanotubes are often visualised as rolled-up sheets of carbon atoms, that is not how they are made. Rather, scientists employ a method known as arc-discharge, which begins with a chamber that is filled with a non-reactive gas.

Two electrodes – rods of graphite, a pure form of carbon – are inserted into the chamber, and an electric charge is applied. When the two rods are brought close together, the intense energy of the resulting spark vaporises one of their tips. Upon examination of the other rod’s tip, one finds that microscopic, stringy protrusions have formed, resembling a tousled head of hair. Those protrusions are carbon nanotubes, specifically multi-walled ones that typically contain 20-30 walls. If a metal catalyst is included in the positively charged graphite rod (the anode) then single-walled carbon nanotubes form.

The inventor

Sumio Iijima has worked in the field of material sciences for over half a century and is the recipient of numerous awards and honorary degrees. He is often credited with the discovery, and at the very least the popularisation, of both multi- and single-walled nanotubes. For his own part, Iijima says he shares the discovery with a few teams of scientists who had previously observed but never fully pursued hollow, graphite carbon tubes.

Iijima is a professor at Meijo University in Nagoya and continues to work as a Senior Research Fellow at NEC Corporation. He is also an honorary fellow at Japan’s National Institute of Advanced Industrial Science and Technology.

Did you know?

In 2006, German researchers found carbon nanotubes in the renowned Damascus steel of the 17th century, accounting for that city's legendary sword making. Another product that incorporates carbon nanotubes is Vantablack, the blackest substance on earth. This material is marketed by the UK nanotech company Surrey NanoSystems for astronomical and military applications. One of its uses is to coat the inside of telescopes to absorb excess light. It is also employed to calibrate cameras that take pictures of very dim stars and galaxies.