A research team from the University of Illinois who have developed a way to manufacture nanowires of any length
from various materials. Not, unfortunately, carbon nanotubes, or we
would be looking for news on space elevators soon. The process is
analogous to drawing with a fountain pen — as liquid is drawn from a
reservoir, a solvent (water or an organic) evaporates and the solute
precipitates onto a substrate.

http://library.thinkquest.org/05aug/01179/silica_nanowire.jpg

The continuous
fabrication of complex, three-dimensional nanoscale structures and the
ability to grow individual nanowires of unlimited length are now
possible with a process developed by researchers at the University of
Illinois.

Based on the rapid evaporation of solvent
from simple “inks,” the process has been used to fabricate freestanding
nanofibers, stacked arrays of nanofibers and continuously wound spools
of nanowires. Potential applications include electronic interconnects,
biocompatible scaffolds and nanofluidic networks.

“The process is like drawing with a fountain pen – the ink comes out
and quickly dries or ‘solidifies,’ ” said Min-Feng Yu, a professor of mechanical science and engineering, and an affiliate of the Beckman Institute. “But, unlike drawing with a fountain pen, we can draw objects in three dimensions.”

Yu and graduate students Abhijit Suryavanshi and Jie Hu describe the
drawing process in a paper accepted for publication in the journal
Advanced Materials, and posted on its Web site.

To use the new process, the researchers begin with a reservoir of ink
connected to a glass micropipette that has an aperture as small as 100
nanometers. The micropipette is brought close to a substrate until a
liquid meniscus forms between the two. As the micropipette is then
smoothly pulled away, ink is drawn from the reservoir. Within the tiny
meniscus, the solute nucleates and precipitates as the solvent quickly
evaporates.

So far, the scientists have fabricated freestanding nanofibers
approximately 25 nanometers in diameter and 20 microns long, and
straight nanofibers approximately 100 nanometers in diameter and 16
millimeters long (limited only by the travel range of the device that
moves the micropipette).

To
draw longer nanowires, the researchers developed a precision spinning
process that simultaneously draws and winds a nanofiber on a spool that
is millimeters in diameter. Using this technique, Yu and his students
wound a coil of microfiber. The microfiber was approximately 850
nanometers in diameter and 40 centimeters long.

To further demonstrate the versatility of the drawing process, for
which the U. of I. has applied for a patent, the researchers drew
nanofibers out of sugar, out of potassium hydroxide (a major industrial
chemical) and out of densely packed quantum dots. While the nanofibers
are currently fabricated from water-based inks, the process is readily
extendable to inks made with volatile organic solvents, Yu said.

“Our procedure offers an economically viable alternative for the
direct-write manufacture of nanofibers made from many materials,” Yu
said. “In addition, the process can be used to integrate nanoscale and
microscale components.”

The Grainger Foundation, the National Science Foundation and the Office
of Naval Research provided funding. Part of the work was carried out in
the university’s Center for Microanalysis of Materials, which is partially supported by the U.S. Department of Energy.

http://www.news.uiuc.edu/WebsandThumbs/Yu,Min_Feng/yu_minfeng_b.jpg

Min-Feng
Yu, a professor of mechanical science and engineering, and an affiliate
of the Beckman Institute, has developed a new process for creating
complex, three-dimensional nanoscale structures.

Via University of Illinois

To reach Min-Feng Yu, call 217-333-9246; e-mail: [email protected].