Researchers at a US university have discovered a method to make highly-aligned nanotube films, that may become valuable for flexible electronics and photonic devices.
A simple filtration process helped researchers at the Rice University create flexible, wafer-scale films of highly aligned and closely packed carbon nanotubes.
Scientists at Rice, with support from Los Alamos National Laboratory, have made inch-wide films of densely packed, chirality-enriched single-walled carbon nanotubes through a process revealed today inNature Nanotechnology.
In the right solution of nanotubes and under the right conditions, the tubes assemble themselves by the millions into long rows that are aligned better than once thought possible, the researchers reported.
The thin films offer possibilities for making flexible electronic and photonic (light-manipulating) devices, said Rice physicist Junichiro Kono, whose lab led the study.
Think of a bendable computer chip, rather than a brittle silicon one, and the potential becomes clear, he said.
"Once we have centimeter-sized crystals consisting of single-chirality nanotubes, that's it," Kono said.
"That's the holy grail for this field. For the last 20 years, people have been looking for this."
The Rice lab is closing in, he said, but the films reported in the current paper are "chirality-enriched" rather than single-chirality.
A carbon nanotube is a cylinder of graphene, with its atoms arranged in hexagons.
How the hexagons are turned sets the tube's chirality, and that determines its electronic properties.
Some are semiconducting like silicon, and others are metallic conductors.
A film of perfectly aligned, single-chirality nanotubes would have specific electronic properties.
Controlling the chirality would allow for tunable films, Kono said, but nanotubes grow in batches of random types.
For now, the Rice researchers use a simple process developed at the National Institute of Standards and Technology to separate nanotubes by chirality.
While not perfect, it was good enough to let the researchers make enriched films with nanotubes of different types and diameters and then make terahertz polarizers and electronic transistors.
