[Editors] MIT: Spinning at the nanoscale

[Elizabeth Thomson]

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MIT: Spinning at the nanoscale
--Electrospun fibers could be used for protective clothing, wearable  
power and more
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For Immediate Release
TUESDAY, MAY. 5, 2009

Contact: Elizabeth A. Thomson, MIT News Office
E: thomson at mit.edu, T: 617-258-5402

Photo Available

CAMBRIDGE, Mass.--In his office, MIT Professor of Chemical Engineering  
Gregory Rutledge keeps a small piece of fabric that at first glance  
resembles a Kleenex. This tissue-like material, softer than silk, is  
composed of fibers that are a thousand times thinner than a human hair  
and holds promise for a wide range of applications including  
protective clothing, drug delivery and tissue engineering.

Such materials are produced by electrospinning, a technique that has  
taken off in the past 10 years, though the original technology was  
patented more than a century ago. In Rutledge’s lab, researchers are  
exploring new ways to create electrospun fibers, often incorporating  
materials that add novel features such as the ability to kill bacteria.

“We’re still in the Wild West mode of discovery,” says Rutledge.  
“People are hypothesizing almost anything and giving it a try. We’re  
still trying to figure out which ones are the payoff applications.”

Rutledge has been one of the pioneers of electrospinning nanofibers  
since the nanotechnology boom of the late 1990s. Though he describes  
the actual electrospinning process as almost “a mundane thing,” he and  
his colleagues have demonstrated a number of ways to create  
electrospun membranes with new and useful traits.

Electrospinning, the most general way to make a continuous polymer  
nanofiber, uses an electrical charge to draw the fiber from a liquid  
polymer. As a jet of charged fluid polymer sprays out the bottom of a  
nozzle, an electric field forces the stream to whip back and forth,  
stretching the fiber lengthwise so its diameter shrinks from 100  
microns to as little as 10 nanometers.

The fiber forms a thin membrane as it hits the surface below the  
nozzle. These electrospun membranes have a unique combination of  
stretchiness and strength, and are easy to handle, making them  
suitable for a wide range of applications. Because the membranes are  
very porous (they contain 85 percent open space), they are already  
used as HEPA (high efficiency particle accumulation) filters, found in  
vacuum cleaners and military tanks.

In the past few years, Rutledge’s team has produced several textiles  
that incorporate functional materials into the electrospun membranes.  
One major focus is designing textiles that can protect against toxic  
agents, both biological and chemical, by adding protective compounds  
to the polymer.

One such material, described in the journal Polymer last year,  
incorporates chlorhexidine, which can kill most bacteria. Rutledge’s  
team is also working with oximes, a class of organic compounds that  
can break down organophosphates, chemicals that are the basis of many  
pesticides, insecticides and nerve gases. Materials such as these,  
developed in collaboration with Alan Hatton, the Ralph Landau  
Professor of Chemical Engineering, could be used to coat medical  
devices or create protective clothing for soldiers.

Rutledge and Paula Hammond, the Bayer Professor of Chemical  
Engineering, recently reported in the journal Advanced Materials a  
material embedded with titanium oxide, which can break down a variety  
of industrial chemicals, including organic compounds like phenols and  
allyl alcohol.

The fibers hold promise for development of new breathable, waterproof  
materials. Four years ago, Rutledge and Randy Hill of Dow Corning  
created an electrospun sheet that is extremely water-repellent. Such a  
material, described in the journal Langmuir, has the potential to  
become a cheaper alternative to GoreTex, which is made of Teflon — a  
more expensive starting material than the polymers used to make  
electrospun fibers.  More recently, working with MIT professors Karen  
Gleason, Robert Cohen, Gareth McKinley and Michael Rubner, Rutledge’s  
group has demonstrated a variety of ways to render breathable  
electrospun fabrics water- and oil-repellent.

Rutledge is now working on electrospun fibers made of block copolymers  
that self-assemble into a collection of concentric cylinders within  
the fiber. Such fibers, made possible by a co-axial version of  
electrospinning technology that the group reported in 2004, could be  
used to impart color to fabrics without dye, or to create “wearable  
power” by combining electrodes and electrolytes into individual fibers.

“There are a lot of ways one can imaginatively think to use some of  
this stuff,” says Rutledge.

--END--

Written by Anne Trafton, MIT News Office
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