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University of Iowa News Release

Nov. 30, 2004

Researchers Make Discovery In Semiconducting Polymers

A team of University of Iowa researchers has discovered that the electrical resistance of semiconducting polymer devices is unusually sensitive to magnetic fields. In addition, team members believe that a device of their design, an electrical resistor, has the potential to revolutionize the multibillion-dollar market for computer display screens, computer storage units and related items, according to an article published Nov. 30 in the "New Journal of Physics."

Markus Wohlgenannt, assistant professor in the UI College of Liberal Arts and Sciences Department of Physics and Astronomy, says that the device, for which the university has filed a patent, holds great promise.

"We have discovered what is, to the best of our knowledge, the most sensitive magnetoresistive (MR) device for the measurement of small magnetic fields at room temperature," he says. His colleagues include: physics and astronomy doctoral student Omer Mermer and Thomas Francis and G. Veeraraghavan, both graduate students in the UI College of Engineering Department of Electrical and Computer Engineering.

Wohlgenannt adds that the MR device is based on relatively novel kinds of materials, called organic semiconductors, used primarily in display applications and, in particular, organic light-emitting diodes (OLEDs). Commercial applications of MR devices include the vibrant research and development area of the magnetic storage of information, such as hard disks, magnetic tape, videotape and magnetic RAM.

"Most previously known MR effects, such as classical magnetoresistance, are too small for practical application, but the MR effect we have discovered in plastics is about 10 percent and among the largest known to date," Francis says.

"The polymer devices we describe can be manufactured cheaply on flexible substrates, such as plastics, and are transparent and light-weight. Our MR devices are compatible with the processing techniques likely to be used in the next generation of flat panel computer screens (e.g. OLED screens). Therefore the MR sensors may be easily integrated into the displays to allow for added functionalities, such as touch-screen capability. The user would be able to interact with the screen through the use of a magnetic pen. Other possible device applications include magnetic random access memory and multi-read head hard disk drives. The fact that our MR devices are cheap to manufacture opens up applications in areas such as disposable products and toys," Wohlgenannt says.

"The Physics and engineering of MR devices is under intense investigation in industry, national laboratories, and universities, and the devices represent a $150 billion per year market, including $50 billion per year for non-tape-based magnetic storage," he says. "Commercial applications of OLEDs include a wide variety of products in the area of lighting and display industry. According to the U.S. Department of Energy, the two technologies which hold the most promise for application to general illumination are LEDs and OLEDs.

"Our discovery is very intriguing from a scientific point of view. Most other MR sensors are made from magnetic materials like iron. Our devices do not contain any magnetic materials. The effect is therefore related to the peculiar mode of charge transport in organic semiconductors, a field that still relatively little is known about. We feel that if we find an explanation for this effect, this will lead to a breakthrough in the scientific understanding of organic semiconductors," Wohlgenannt says.

The article in the journal -- New J. Phys. 6 (2004) 185 -- can be found online at

STORY SOURCE: University of Iowa News Services, 300 Plaza Centre One, Suite 301, Iowa City, Iowa 52242-2500.

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