Carbon nanotubes can create working circuits through the use of a special pen that easily creates the devices.
Flexible circuits are created using nanotubes each nearly 20 inches long.
Fiber drawing has been accomplished before, but the nanotubes were extremely short - just a small fraction of an inch - limiting their use in electronic devices. Traditional technology also takes long periods of time to create, which adds to costs and manufacturing challenges. The new pen can create working circuits at a rate of around four inches per second.
Tsinghua University researchers in Beijing, China developed the new technology, which creates circuits that are both flexible as well as highly conductive.
The ink is created from carbon nanotube fibers in a solution of polyethylene oxide (PEO), a viscous polymer. The electrically-conductive tubes are drawn through the pen by the PEO, a material with significant chemical strength.
"The drawing technique allow us to achieve very long carbon nanotube fibers mainly due to the high molecular weight of the polymer and high viscosity of the precursor solution as ink," Hui Wu from Tsinghua University said.
Nanotube fibers are created by users through lifting the pen, and are then laid out in the desired surface. Fairly precise arrangements can be created by hand, and researchers believe even more intricate designs will be possible using advanced manufacturing equipment.
The nanotube fibers become even more electrically conductive after bending, a result which surprised developers. Tests showed the material became 30 percent more conductive after being bent 1,000 times. It is possible that flexing alters the shape of the polymer, creating more efficient arrangements of the nanotubes in the fiber. Thinner fibers are more efficient at transmitting electrical signals than thicker ones, due to the molecular arrangement of nanotubes within the polymer.
Although the nanotube-infused ink is new, the pen used to apply the material is a standard commercial instrument, which could lower costs for future version of the substance.
Flexible electronic devices, including solar cells and touch displays, could be created using the new pen. Batteries are among the most challenging devices to design for new wearable technologies, but a new lithium-ion battery uses a yarn made of nanotubes to develop usable cells.
Further development of the fibers could result in the creation of various inks, each designed for specific applications.
"We are now working on enabling more functions in the fiber. For example, one possibility is semiconducting fibers drawn from a pen tip for flexible device applications," Wu told the press.
Development of the new nanotube fibers was published in the journal Nano Letters.
