Stanford researchers have found an effective way to sort carbon nanotubes, making progress towards flexible or printable electronics.

When carbon nanotubes are created, both semi-conducting and conducting tubes are mixed together. Conducting tubes are used in wires and electrodes. Semiconducting tubes are more adept in things like solar technologies; however, the combination of the two makes it difficult to utilize them for both purposes. For example, using the mixture in electronics often causes shortages and has stymied advances in nanotube technology.

Zhenan Bao, Stanford associate professor of chemical engineering, worked with professors at University of California-Davis and the Samsung Advanced Institute of Technology (SAIT) and has discovered a way to separate the mixture and pull out the conducting and semi-conducting tubes individually.

“Sorting has been a major bottleneck for carbon nanotubes to be viable for practical electronics applications,” Bao said in an interview with the Stanford Report. “This work solves the problem of separating the conducting from the semi-conducting nanotubes.”

Bao added a polymer to the mixture that only attaches itself to the semi-conducting nanotubes, allowing commercially available packages of mixed carbon nanotubes to be separated effectively.

This is not the first polymer that is able to sort the semi-conducting and conducting nanotubes; however, previous polymers have had to be removed before the nanotubes could be conductive again. Bao’s polymer doesn’t need to be removed and doesn’t decrease the nanotube’s conductivity.

“It merges two very important materials together and makes a hybrid material that could be very useful for printed and flexible electronics,” Bao said.

Funding for the study came from the SAIT and the National Science Foundation.

–Brendan O’Byrne