Transparent nano-fibre film can be designed to conduct electricity, repel dirt,
attract oil
19 July 2007 A new technique for making a film of tiny plastic fibres with
customisable properties could lead to new products as diverse as transparent
electronic devices, self-cleaning surfaces and biomedical tools that
manipulate strands of DNA.
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A scanning electron microscope image of plastic
fibers grown on a sheet of transparent film.
Image courtesy of Ohio State University. |
The patent-pending technology
developed by researchers at Ohio state University involves growing a
bed of fibres of a specific length, and using chemical treatments to tailor
the fibres' properties. When seen with the naked eye the surfaces look as
flat and transparent as a sheet of glass. But seen up close, the surfaces
are actually carpeted with tiny fibres. The research was published in the
June issue of the journal Nature Nanotechnology. Arthur J. Epstein,
Distinguished University Professor of chemistry and physics and director of
the university's Institute for Magnetic and Electronic Polymers, said "One of the
good things about working with these polymers is that you're able to
structure them in many different ways. Plus, we found that
we can coat almost any surface with these fibres." For this study, the
scientists grew fibres of different heights and diameters, and were able to
modify the fibres' molecular structures by exposing them to different
chemicals.
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| A drop of water balances perfectly on a film of
plastic nanofibres. Photo credit; Jo McCulty, courtesy of Ohio State
University. |
Different treatments made the fibres repel or attract water or oil. Depending on
the polymer used, the fibres can also be made to conduct electricity or
attract strands of DNA. When the researchers put droplets of water containing DNA on
the fibres, the strands uncoiled and hung suspended from the fibres like
clotheslines. Epstein said scientists could use the fibres as a platform
to study how DNA interacts with other molecules. They could also use the
spread-out DNA to build new nanostructures. "We're very excited about
where this kind of development can take us," said Epstein, whose research
centres on polymers that conduct electricity, and light up or change colour.
Depending on the choice of polymer, the nano-fibre surface can also conduct
electricity. The researchers were able to use the surface to charge an
organic light-emitting device — a find that could pave the way for
transparent plastic electronics. Finally, they also showed that the fibres
could be used to control the flow of water in microfluidic devices — a
speciality of study co-author L. James Lee, professor of chemical and biomolecular engineering and head of Ohio State's Center for Affordable
Nanoengineering of Polymeric Biomedical Devices. The technology is a merger of two different
chemical processes for growing polymer molecules: one grows tiny dots of
polymer 'seeds' on a flat surface, and the other grows vertical fibres out
from the top of the seeds. The fibres grow until the scientists cut off the
chemical reaction, forming a carpet of uniform height. The university will
license the technology, and Epstein and his colleagues are looking for new
applications for it. Lee and Epstein are advisors to former graduate
student Nan-Rong Chiou, who developed the technology to earn his doctorate. Aside from anti-fog windows, self-cleaning windows,
and organic LEDs, Chiou said that he foresees the surfaces working in
glucose sensors, gene therapy devices, artificial muscles, field emission
displays, and electromagnetic interference shielding. To top
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