World's Smallest Transistor Radio

New Nanotube Fabrication System Shows Practical Applications

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.