Polymeric nanofibers have a promising future in exotic applications such as medical implants, flat-panel televisions and solar cells, according to three University of Akron professors.
Another professor, from the State University of New York at Stony Brook, explained how membranes made of nanofibers can purify water.
The fiber experts spoke May 17 at a new technology forum on polymers for conservation of a clean environment during Antec 2010 in Orlando.
Mike Cakmak described a special machine the university made that can form a network of connected fibers, by partially embedding them into cast film. The Akron, Ohio, university got a grant from Ohio's Third Frontier program to build the roll-to-roll manufacturing equipment.
The process can turn out flexible films that are electrically conductive, said Cakmak, distinguished professor of polymer engineering. He said the university is working with some companies to commercialize the technology.
In Akron, university technicians built what Cakmak called a hybrid machine that does both electro-spinning of fibers and solution casting, in a continuous process. First, banks of electro-spinning devices produce the fibers, which then get embedded into cast film before they are cured. Two drums turn a belt that moves the material through the stages.
Roll-to-roll technology can use a polymer solvent, which must be removed by evaporation, or curing with ultraviolet light.
The result, Cakmak said, is a thin sheet of transparent, flexible fibers that can be bent into sharp curves while remaining electrically conductive. That opens up brand-new possibilities for fibers such as flexible batteries and printed electrical circuits, and what he called stretchable electronic implants. Other applications include solar cells and liquid crystal displays.
Darrell Reneker, UA professor of polymer science, presented electro-spinning 101. He played videos showing the fibers coming out of an electrified jet. The nanofibers have a large surface area per gram of weight making them excellent for creating very thin filters. You can also package cells or spores into the fiber mesh, creating medical products.
Reneker even said that, in the future, electro-spun fibers could play a role in huge solar sails that act like mirrors in space to propel spacecraft.
Microscopic fibers also could play a key role in filtering out automotive and industrial pollution like nitrogen oxides and carbon monoxide, according to George Case, a UA professor of chemical and biomolecular engineering. He said there are two ways to apply nanofibers in a filter media: add a layer of nanofibers onto the surface of a commercial microfiber material, or mix non-fiber material among the microfiber.
Benjamin Chu, of SUNY at Stony Brook, N.Y., explained advances in the nanofiber technology to purify drinking water.
These kinds of problems are big problems, said Chu, distinguished professor of chemistry, who noted global population growth and the prevalence of waterborne illnesses. Clean drinking water is an important global problem, and this is how to purify water cost effectively.
Many current water-purification technologies are very expensive, he noted.
A mesh made of a sandwich of a support structure, a nanofiber scaffold support and a coating can create a filter that has flux capacity at low operating pressures, but retains a resistance to fouling, he said.
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