Stanford researchers debut first robot run by carbon nanotube transistors

March 7, 2013, 11:55 p.m.

A group of Stanford researchers recently debuted the first robot controlled by a computer chip built entirely from carbon nanotube transistors, which many scientists predict may eventually replace silicon.

While scientists have produced simple demonstrations of working carbon nanotube circuit components in the past, the Stanford team, led by Professor of Electrical Engineering Philip Wong and Associate Professor of Electrical Engineering and Computer Science Subhasish Mitra Ph.D. ’00, was able to demonstrate an actual subsystem composed entirely of the material.

The project was presented in the form of a robot named Sacha at the 2013 International Solid-State Circuits Conference, which was held in San Francisco. According to Mitra, the robot was created to demonstrate the development of a system that can function despite the errors caused by inherently imperfect nanotubes, which have posed issues for research teams working with carbon nanotubes in the past.

“One thing we could have done was to bring out our lab equipment [to the conference], but that’s not really effective,” Mitra said. “That’s why we came up with the idea of making a robot which people can actually see and interact [with].”

Mitra said that the use of carbon nanotubes directly tackles one of the greatest challenges currently facing the electronic systems industry—energy efficiency. According to Mitra, one of the next steps in working with nanotubes is to demonstrate that the energy benefits from nanotubes derived at the level of transistors and small circuits are also present at the larger subsystem level.

Max Shulaker ’12 Ph.D. ’17, who participated in the robot demonstration, has been working with carbon nanotubes since his freshman year at Stanford. According to Shulaker, research on carbon nanotubes is important because of the material’s potential role in furthering Moore’s Law, which states that every 18 months, the size of a computing device is halved.

“Things get smaller, better and more efficient. We’re reaching that point where we can’t make things smaller,” Shulaker said. “Carbon nanotubes are the step after making things smaller. This can be something to keep Moore’s Law going—to keep improving computing power.”

Supratik Guha, director of physical sciences at IBM’s Yorktown Heights Research Center, shared Shulaker’s optimism about the potential of carbon nanotubes.

Guha said that IBM has worked with carbon nanotubes for 15 years. While their efforts were initially focused on developing carbon nanotubes, IBM scientists have now focused on the use of carbon nanotubes in nanoscale devices as a replacement for silicon.

“Through several generations of technology, devices keep getting smaller and denser, and silicon will no longer be the best material for the purpose in about ten years,” Guha said. “For needs that are close to atomic dimensions, carbon nanotubes have just the right shape and the right electrical behavior.”

Shulaker agreed that carbon nanotubes cannot yet replace silicon, but said that all of the Stanford researchers’ work is silicon-compatible.

“That’s completely intentional, because we realize that there’s so much money and so much drive behind silicon that replacing it straightaway is infeasible, but the gradual introduction of CNTs [carbon nanotubes] to supplement silicon is very feasible,” he said.

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