14 DAY TRIAL // A group of experts at the Rice University in the United States announces the development of a new method for producing the famous field-effect transistors (FET), the basic units of integrated circuits that make advanced electronic devices possible. The scientists say that they used ink-jet printers to produce thin films of carbon nanotubes, which can then be readily used to produce the FET. These transistors go into microprocessors today, but they hold great promise for being used in flexible substrates for advanced electronics tomorrow, the team says,
The Rice group says that their method is not capable of producing the FET at the level of miniaturization required for current microprocessors, but add that the technique should come in handy for numerous manufacturers and companies looking to print electronics on various substrates, including the flexible variety. Details of the investigation appear in a recent online issue of the esteemed scientific journal ACS Nano. Researchers in Mexico, Spain and Finland also contributed to the work, which relied heavily on using custom-made inks to create the nanotubes.
“The key is printing the appropriate number of layers to get the type of conduction you want, either metallic or semiconductive,” explains Robert Vajtai, who is a faculty member at the Rice Mechanical Engineering and Materials Science Department, and also the leader of the current research. His coauthor was the Rice Benjamin M. and Mary Greenwood Anderson professor in mechanical engineering and materials science, Pulickel Ajayan. The team says that increasing the number of nanotube layers they printed on substrates gradually increased conductivity, as well as the number of connections between the nanotubes themselves. A single layer, the experts say, is unable to conduct electricity very efficiently.
“This is not a perfect transistor, but it is applicable in digital electronics. There are some limitations. I doubt anyone could take a $60 ink-jet printer and print predesigned electronic circuits. But with a high-end printer, it is a fairly straightforward process and allows you to put together whatever you want,” the team leader explains. “Say you want to have a raincoat made with transistors – doing whatever a raincoat needs to do that requires electricity, such as controlling and analyzing signals from several sensors and light sources, for safety. It can be done,” he concludes.