You could say Morinobu Endo is one of the fathers of the carbon nanotube. Even though he didn’t call his intellectual offspring by that name, he began working with carbon nanotubes and related materials in the mid-1970s, back when the “micro”-scale was still the latest thing. He published a seminal paper in 1976 that explained how to make them.
He’s been playing with them ever since, figuring out how to manufacture them more rapidly and cheaply and how to integrate them into useful objects. His research has resulted in ten-fold annual increases in the quantity of nanotubes that can be made with his process and also in vast quality-control improvements.
His publication list contains page after page of papers on various aspects of nanotube manufacturing with forays into application areas as well. One recent publication focused on using nanotubes in medical catheters. Without his work nanotubes might be just another carbon oddity rather than the intriguing and promising material they’ve become.
But Endo’s nanotubes might not have happened without the right sandpaper. Back in the 1970s, Endo was experimenting with making carbon deposits through chemical vapor deposition. To save time between experiments, he tried to clean the resulting soot off the substrate with sandpaper rather than washing it and drying it for two days. To his surprise the sanded substrate produced carbon fibers the next time it was used. But not always. Black silicon carbide paper didn’t yield anything, yet the fibers grew splendidly on a substrate treated with brown sandpaper containing iron oxide particles. Each tube had an iron oxide particle at one end. He realized it was a critical catalyst for forming the nanotubes. Endo later developed a more efficient method of seeding the substrate with iron oxide particles, which yielded a bumper crop of tubes. Unfortunately the technique was expensive – the tubes cost about $2,000 per kilo.
Morinobu Endo, professor of engineering at Shinshu University in Nagano, Japan, discovered key processes for making carbon nanotubes like the catalytic process shown here. Photos courtesy of Morinobu Endo
The real manufacturing breakthrough came when Endo read a newspaper article about an influenza epidemic in Tokyo and the dangers of coming within range of a sneeze from an infected person. It occurred to him that the iron oxide nanoparticles were lighter than the flu viruses that floated so well in the air, and that the particles would suspend in air even better. It turned out that the floating particles produced nanotubes just fine and in much higher volume than previous methods. That development led to commercialization of multi-walled carbon nanotubes nicknamed “Endo fibers,” which are used in lithium-ion and lead acid batteries to prolong their lifetime.
An engineering professor at his alma mater, Shinshu University in Nagano, Japan, Endo today runs a research group whose work runs the gamut from basic science to applications. Not surprisingly the group’s work includes carbon nanotubes, new forms of carbon and graphite, nanoporous carbons, lithium-ion batteries and electric double-layer capacitors. He has authored or co-authored more than 40 textbooks and 250 papers in prestigious journals including Nature, Science and Physical Review. He chairs the Japan Carbon Society and serves on the advisory board of Carbon Journal. He has received a long list of awards and honors, both in Japan and internationally, including the 2004 American Carbon Society Medal.