Nancy Huang

Oct 6th 2021

Sumio Iijima: Inventor of Carbon Nanotubes and Pioneer of Modern Tech


Often, the small-scale or hidden technologies that make modern life work are the easiest to overlook — and those who discover them sometimes don’t get the spotlight they deserve.

Sumio Iijima is a Japanese physicist and inventor who was the first to clearly describe the formation of carbon nanotubes and imagine their potential. Iijima’s 1991 discovery and subsequent work sparked a revolution in nanotechnology, which uses materials measured in nanometers (one billionth of a meter). Now, nanotechnology is becoming ubiquitous in modern life, with use in electronics, cars, medical devices and many more applications.

The Early Life of an Exemplary Scientist

In 1939, Sumio Iijima was born in rural Saitama Prefecture, which is now considered a suburb of Tokyo.

“I loved nature,” he explained when asked about his childhood in an NEC article. “I collected plants and insects, I fished, and I kept a menagerie of small animals, including pigeons, rabbits, snakes, frogs, and crabs. I learned many things from my experiences with nature, and I believe that this helped me develop both sensitivity and insight. In high school and university, I was in the mountaineering club and the music club, and spent my youth exploring nature and challenging the limits of my creativity.”

With all of these outside interests, his classroom work took a back seat in his formative years.

“I didn’t have very good grades … because I never studied,” Iijima told Bloomberg. He ended up failing his university entrance exams.

Iijima spent a year “memorizing facts” to pass the exams and was accepted into the University of Electro-Communications in Tokyo. Iijima found the school’s focus on communications engineering to be a poor fit for him. After switching to a chemistry major in his last year, Iijima became engaged in his studies.

“For the first time in my life, I studied very hard,” he told Bloomberg. He was accepted into a Master’s Degree program at Tohoku University. Based on the admissions interview, Iijima was placed in a lab that specialized in using high-resolution microscopes to study the atomic structure of materials.

“This one interview determined the rest of my life,” Iijima said. “It wasn’t that I had a particularly strong desire to do research with electron microscopes at the time, but I found that I was perfectly suited to research in the field.”

Iijima’s Career Gains Momentum

Iijima earned a Master’s Degree in 1965 and a PhD in solid-state physics in 1968, both from Tohoku University in Japan. From 1970 to 1982, he was a post-doctoral fellow and senior research associate at Arizona State University. There, he developed high-resolution transmission electron microscopy (HRTEM) with the late Professor John M. Cowley in 1979. HRTEM can show the structure of materials down to the atomic level. At Arizona State, Iijima studied the atomic structure of carbon. He also spent time in 1979 as a visiting senior scientist at the University of Cambridge in England, using electron microscopy to study graphite. All these experiences, especially the development of HRTEM, would play a role in Iijima’s discovery of nanotubes in 1991.

In 1982, Iijima returned to Japan to study ultrafine particles at the Research Development Corporation of Japan (now Japan Science and Technology Agency) as a government employee. In 1987, he joined the NEC Corporation in Tokyo as a research fellow at the age of 47. As Iijima explained in an NEC article, he made the switch because the company “agreed to purchase an expensive, high-performance electron microscope.” His initial work at NEC was focused on cutting-edge semiconductor materials.

Captivated by the Discovery of Nanoscale Spheres

With his background in carbon structures, Iijima was inspired by the 1985 discovery of fullerenes (hollow, nanoscale spheres of pure carbon), which would win the Nobel Prize in Chemistry in 1996. Fullerenes were revealed with electron microscopy methods that Iijima helped to develop. At a 1990 academic conference, Iijima joined a small group that ended up discussing fullerenes late into the night, as he explained to Bloomberg. When he returned to Japan, Iijima immediately started to apply the methods used to create fullerenes to his nanotube experiments.

Less than a year later, Iijima used his trusty electron microscope to observe tiny carbon tubes stacked within tubes, which were the multi-walled carbon nanotubes that would be described in his ground-breaking 1991 Nature paper. These multi-walled nanotubes contained 2 to 50 graphite tubes, with diameters of up to 100 nanometers. In 1993, Iijima discovered that adding a metal catalyst would result in the formation of single-walled carbon nanotubes. His later discoveries would reveal how carbon nanotubes can be capped with fullerenes or intentionally uncapped and how single-walled carbon nanotubes could be prepared without toxic metal catalysts.

The Amazing Attributes of Nanotubes

Carbon nanotubes are man-made materials that consist of flat sheets of pure carbon rolled into tubes with a diameter as small as 0.8 nanometers. The length of a tube can be up to several millimeters (1 millimeter = one million nanometers). Each carbon atom bonds to three other carbon atoms, forming a hexagonal arrangement, similar to a honeycomb. When laid in flat sheets, carbon atoms in a hexagonal arrangement form graphite, a material used in everyday pencils. However, when a hexagonal carbon sheet forms a tube at the nanometer scale, it exhibits unique physical and chemical properties. These properties can vary with the diameter of the tube and the helical orientation of the hexagonal rings within the tube.

These nanotubes are exceptionally light and strong — being one-sixth as dense as steel, but 400 times stronger, according to Nanowerk. They are harder than diamonds (which is another form of pure carbon) and are a better thermal conductor. Carbon nanotubes are chemically stable and very flexible. They can have extraordinary electrical conductivity (1,000 times more conductive than copper) or function as a semiconductor. The tiny space in the tube can carry other nanoscale materials.

It’s hard to overestimate the impact of Iijima’s 1991 Nature paper first describing nanotubes. It ranks #36 in Nature‘s 2014 list of the top 100 most-cited research papers of all time. Iijima has continued to be a highly prolific researcher who is very much in the conversation for a Nobel Prize in physics or chemistry. His awards and honors include the 2002 Japan Academy Award, the 2002 Benjamin Franklin Institute Medal in Physics, the 2008 Navli Prize in Nanoscience and the 2015 European Inventor Award. Microsoft Academic also credits Iijima with 755 publications and 144,885 citations.

Bringing Materials to Market

Sumio Iijima firmly believes that “new materials only have value when they are used.” While carbon nanotechnologies have entered the market, their full potential has not yet been reached. As the European Patent Office explains, current products incorporate bulk nanotubes, which are masses of unorganized nanotubes that are used as composite fibers to bolster mechanical, thermal and electrical properties. These products include smartphone touch pads and a material called Vantablack, known as the blackest substance on Earth, which is used in telescopes and cameras to absorb excess light.

As Iijima explains in an interview for NEC, “We need a technique that orients and aligns the tangled weaves of just-created carbon nanotubes in the same direction” and that allows for mass production. Many companies and research organizations are developing nanotube materials and products, including lightweight but strong industrial materials (e.g. for aircraft hulls), tiny yet powerful computer chips, super compact fuel-cell batteries, highly efficient power lines and drug delivery systems for carrying medications into the body. At 82 years young, Sumio Iijima remains a leader in this nanotechnology research.

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