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Printed Electronics World
Posted on February 9, 2010 by  & 

Carbon nanotube ink turns cloth into a battery

Ordinary textiles could be transformed into batteries that hold up to three times more energy than a mobile phone battery, by simply dipping them into nanoparticle-infused ink.
Conventional batteries are made by coating metallic foil in a particle slurry and rolling it into compact form - a capital-intensive process. The new energy textiles were manufactured using a simple "dipping and drying" procedure, whereby a strip of fabric is coated with a special ink formula and dehydrated in the oven.
"Wearable electronics represent a developing new class of materials... which allow for many applications and designs previously impossible with traditional electronics technologies," said the researchers at Stanford University who are developing the batteries and simple capacitors.
The procedure works for manufacturing batteries or supercapacitors, depending on the contents of the ink - oxide particles such as LiCoO2 for batteries; conductive carbon molecules (single-walled carbon nanotubes, or SWNTs) for supercapacitors. Up to now, the team has only used black ink, but Yi Cui, assistant professor of materials science and engineering at Stanford, said it is possible to produce a range of colors by adding different dyes to the carbon nanotubes.
The lightweight, flexible and porous character of natural and synthetic fibers has proven to be an ideal platform for absorbing conductive ink particles, according to postdoctoral scholar Liangbing Hu, who led the energy textile research. That helps explain why treated textiles make such efficient energy storage devices, he said.
Cui's team had previously developed paper batteries and supercapacitors using a similar process, but the new energy textiles exhibited some clear advantages over their paper predecessors. With a reported energy density of 20 Watt-hours per kilogram, a piece of eTextile weighing 0.3 kilograms (about an ounce, the approximate weight of a T-shirt) could hold up to three times more energy than a cell phone battery.
"The whole thing can be stretchable as well, and extend to more than twice its length," Hu explained. "You can wash it, put it in all kinds of solvents - it's very stable."
They have already received interest from some big-name brands in high performance sportswear and suggest that the military are looking at the possibility of integrating energy textiles into its battle array, a move that could considerably lighten a soldier's load.
Aside from enhanced energy storage capacity, eTextiles are remarkably durable and can withstand greater mechanical stress.
Potential applications range from health monitoring to moving-display apparel. Scientists at the University of Michigan developed a smart fabric that could be used to power a light emitting diode (LED) by dipping cotton fibres into CNT containing water.
Carbon Nanotube Ink Technology is also being developed for use in other areas. Earlier this month SouthWest NanoTechnologies Inc. (SWeNT), introduced Carbon Nanotube Ink Technology for printing large-area, low-cost devices. Applications include energy-efficient lighting, affordable photovoltaics, improved energy storage and printed electronics.
DuPont and Cornell University presented last year a new and relatively simple process to separate metallic and semiconducting carbon nanotubes into a high-performance CNT 'ink' that solely contains semiconducting tubes. Funded by the U.S. Air Force this could prove promising for printed, thin and flexible electronics for TFTs and Photovoltaics.
Reference and Source of top image: Stanford University

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Business Development Director, Research

Posted on: February 9, 2010

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