HOUSTON, May 25 (UPI) -- U.S. scientists say they've made thin films of nanotubes with ink-jet printers to create field-effect transistors -- the basic element in integrated circuits.
While the scientists admitted their technique doesn't exactly scale down to the levels required for modern microprocessors, the Rice University researchers said it will be useful to inventors wishing to print transistors on materials, especially flexible substrates.
The scientists, led by Rice faculty fellow Robert Vajtai and Professor Pulickel Ajayan, said they worked with researchers in Finland, Spain and Mexico using high-end ink-jet printers and custom inks to create their nanotube-based circuitry. They said the process involved analysis of sample circuits printed with single-walled carbon nanotubes functionalized with four types of molecules.
The researchers said they found a single layer of nanotubes-infused ink printed onto a transparent foil didn't conduct electricity very well. But adding layers increased the connections between nanotubes, and so increased conductivity.
"The key is printing the appropriate number of layers to get the type of conduction you want, either metallic or semiconductive," Vajtai said, adding researchers made no attempt to separate metallic from semiconducting nanotubes, which greatly simplified the process.
The research was reported in last week's online edition of the journal Nano.
