Posted in | Nanomaterials

Transparent Transistors Developed For E-Paper and Flexible Screens

Researchers have used nanotechnology to create transparent transistors and circuits, a step that promises a broad range of applications, from e-paper and flexible color screens for consumer electronics to "smart cards" and "heads-up" displays in auto windshields.

The transistors are made of single "nanowires," or tiny cylindrical structures that were assembled on glass or thin films of flexible plastic.

"The nanowires themselves are transparent, the contacts we put on them are transparent and the glass or plastic substrate is transparent," said David Janes, a researcher at Purdue University's Birck Nanotechnology Center and a professor in the School of Electrical and Computer Engineering.

Other researchers had previously created nanowire transistors, but the metal electrodes in the transistors were non-transparent, which made the overall structure opaque, said Tobin J. Marks, the Vladimir N. Ipatieff Professor of Chemistry and a professor in the Department of Materials Science and Engineering at Northwestern University.

"Our study demonstrates that nanowire electronics can be fully transparent, as well as flexible, while maintaining high performance levels," Marks said. "This opens the door to entirely new technologies for high-performance transparent flexible displays."

Findings were detailed this month in a research paper in the journal Nature Nanotechnology.

The advancement has three broad areas of potential applications:

  • Transparent displays for uses such as heads-up displays on windshields and information displays on eyeglasses and visors. The displays enable drivers to see information without looking down at the dashboard and could project information on visors for workers without obstructing their view. Potential applications also include sports goggles for spectators to follow a particular player while having relevant statistics displayed and real-time interactive information for soldiers and surgeons.
  • Flexible displays for future "e-paper," promising to allow full-motion video. E-paper is a technology designed to mimic regular ink on paper. Unlike conventional flat-panel displays, which use a backlight to illuminate pixels, e-paper reflects light like ordinary paper and is capable of holding text and images indefinitely without drawing electricity while allowing the image to be changed later. Potential uses of e-paper include low-cost, energy efficient ways of displaying information and video as a replacement for paper in magazines, newspapers, books, electronic signs and billboards.
  • Transparent and flexible electronics for radio frequency identification tags, electronic bar codes and smart credit cards, which resemble ordinary credit cards but contain an embedded microprocessor. This microprocessor replaces the usual magnetic strip on a credit or debit card, increasing the security of data stored on the card and enabling computers to "talk" to the microprocessor. Such a technology could be used to display balances on cards and could be used for the free flow of people through transportation systems, avoiding the need of ticketing machines or validation gates. The cards could contain encryption software, secure data for use in pay phones and banking, and to contain health-care data for patients and allow tamper-proof identification information for workers.

The nanowires were made of zinc oxide or indium oxide.

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