Monday, July 02, 2007

Invisible nano-fibres

New Invisible Nano-fibers Conduct Electricity, Repel Dirt

A drop of water balances perfectly on a plastic surface invented by researchers at Ohio State University. The surface is covered with microscopic fibers, and can be made to attract or repel water. The surface shown here is water repellant, so the drop can't spread out along the surface; instead, it retains its spherical shape. (Credit: Photo by Jo McCulty, courtesy of Ohio State University)
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They devised one treatment that made the fibers attract water, and another that made the fibers repel water. They found they could also make the surfaces attract or repel oil. Depending on what polymer they start with, the fibers can also be made to conduct electricity.

The ability to tailor the properties of the fibers opens the surface to many different applications.
Since dirt, water, and oil don't stick to the repellant fibers, windows coated with them would stay cleaner longer. In contrast, the attracting fibers would make a good anti-fog coating, because they pull at water droplets and cause them to spread out flat on the surface.

What's more, researchers found that the attracting surface does the same thing to coiled-up strands of DNA. When they put droplets of water containing DNA on the fibers, the strands uncoiled and hung suspended from the fibers like clotheslines.

The patent-pending technology involves a method for growing a bed of fibers of a specific length, and using chemical treatments to tailor the fibers' properties, explained Arthur J. Epstein, University Professor of chemistry and physics and director of the university's Institute for Magnetic and Electronic Polymers.

Epstein's research centers on polymers that conduct electricity, and light up or change color. Depending on the choice of polymer, the nano-fiber 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 fibers could be used to control the flow of water in microfluidic 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 fibers out from the top of the seeds. The fibers 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.

Original Source: Ohio State University

Spider and water bubbles courtesy of Annelisa @ Words that flow