New technique spins superlong nanowires

Fibers are millionths of a millimeter across and kilometers long

In a feat that puts Rumpelstiltskin to shame, scientists have spun a multitude of high tech materials into bundles of superfine nanowires that are more than 1000 meters long. The new technique, reported online June 12 in Nature Materials, easily produces uniform, orderly arrays of gossamer-thin materials that could have broad use in sensors, energy-harvesting devices and medical diagnostics.

ALL WOUND UP Within this pencil-wound, 10-meter stretch of nanowire are hundreds of even smaller wires (shown in cross section). Such wires-within-wires might have broad uses in electronics, sensors and other devices. M. Yaman et al/Nature Materials 2011

It’s not often that the prefixes nano and kilo, which span 12 orders of magnitude, come together, says study leader Mehmet Bayindir of the Institute of Materials Science and Nanotechnology at Bilkent University in Turkey. But a modern take on the spinning wheel allowed Bayindir and his team to draw nano threads that are mere billionths of a meter across out to kilometer lengths.

The work is another step forward in science’s mastery of tiny materials for big, bold applications. While there has been a lot of success in fabricating nanosized materials from similarly small ingredients, it has been harder to trim big bulky starting materials down to nanosize. This spring, MIT researchers successfully created semiconducting wires embedded in a fiber by tweaking a top-down setup that’s employed in industry to make spools of polyester.

Now Bayindir and his colleagues have taken a similar approach. They started with a solid rod of material wrapped in a sturdy polymer. This bulk rod, about 10 millimeters across, is then softened with heat and drawn out in a long thread, yielding wire that’s micrometers across. These threads are then cut down to 10-centimeter lengths and consolidated into a bundle, which is then heated and spun into an even finer thread of threads: A cross section reveals a tidy arrangement of wires within the wire. After a few rounds the team has millions of uniform nanowires that, stacked end to end, would circle the globe.

Not only are the wires exceedingly long (the team is applying to Guinness World Records for the record in nanowire length), but they are also homogeneous. That sameness is precisely what’s needed for applications such as light-sensing or -delivering technologies, and in transistors and other electronic devices.

“In these dimensions, to be able to make a continuous material that’s uniform is critically important,” says materials scientist Satish Kumar of Georgia Tech in Atlanta.

The technique was a success with several materials, the team reports, including semiconducting glass and special polymers that generate an electric field when pressure is applied.

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