World's Smallest Transistor Radio

Scientists at the University of Illinois have built the world's smallest transistor radio according the Early Online Edition of the Proceedings of the National Academy of Sciences released January 29, demonstrating the first practical application of a carbon nanotube technology developed last year.

"These results indicate that nanotubes might have an important role to play in high-speed analog electronics..." said Founder Professor John Rogers of Illinois' Materials Sciences and Engineering program in a press release from Illinois. Rogers is also is a researcher at the Beckman Institute and at the university's Frederick Seitz Materials Research Laboratory.

Working in conjunction with engineers at Northrop Grumman Electronics Systems in Linthicum, Maryland, the team at Illinois used a carbon nanotube growth technique developed in 2007 to produce the various components of the radio, which picked up traffic reports from Baltimore. The fabrication process was developed in a collaborative joint research project involving Illinois, Lehigh and Purdue Universities.

The carbon single-wall nanotube fabrication process allows the precise horizontal alignment of hundreds of thousands of nanotubes. Charges in each tube move independently of the tubes around them, which allows the arrays to be integrated into electronic devices and circuits by conventional chip-processing techniques. Carbon nanotubes have been shown to be more rigorous and capable of withstanding greater physical jostling than silicon-based circuits.

The teams packed seven such nanotube arrays into their miniscule radio, creating a heterodyne receiver in the AM band. Headphones were plugged in directly to the audio amplification nanotube transistor to hear the signal, and in one test picked up radio station WBAL's (AM 1090) traffic report. The device was capable of producing 14 decibels, a quiet, but audible, signal.

"We were not trying to make the world's tiniest radios," Rogers said. "The nanotube radios are a demonstration, an important milestone toward building the technology into a form that ultimately would be commercially competitive with entrenched approaches."

Northrop Grumman is one of the world's largest defense contractors. Their System Development and Technology section searches for and develops emerging technologies in the following missions: Space; Advanced ISR; Strike; Force Protection; Advanced Technology; Network Systems; Surface and Undersea ISR; Cyberwarfare; Navigation; and Homeland Security.

Rogers co-authored the paper with principal author Coskun Kocabas in Illinois' Department of Physics; Hoon-sik Kim and Tony Banks of Material Sciences; and Aaron A. Pesetski, James E. Baumgardner, S. V. Krishnaswamy, and Hong Zhang of Northrop Grumman's Electronic Systems Group. Work was funded by the National Science Foundation and the U.S. Department of Energy.