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E-textiles, robot 'skin' among advances at IEDM

Posted: 13 Oct 2003 ?? ?Print Version ?Bookmark and Share

Keywords:electron devices meeting? organic semiconductor?

The upcoming International Electron Devices Meeting will explore the range of potential applications for crystalline organic semiconductors.

The technology occupies an intriguing niche between high-performance silicon and low-end amorphous silicon or polymer electronics. Like polymers, crystalline organic compounds are carbon-based and thus easy to work with. But like crystalline silicon and other inorganic semiconductors, they have better performance than amorphous compounds, making them attractive for a wider number of applications.

The most prominent application to have emerged thus far is the flat-panel display, where organic light-emitting diodes offer low-cost processing on a variety of substrates. But other application areas, such as radio-frequency ID tags, have yielded some promising developments.

In papers to be presented at IEDM, which will take place in Washington in December, researchers will detail their work on RFID tags, fabrics with integrated electronics and an artificial skin with built-in pressure sensors - all realized with organic, pentacene-based transistors.

The work on RFID tags at 3M Co.'s Electronics and Inorganics Technology Center might hit a market window opening up in the retail-sales sector. Many retailers are pushing to replace bar codes with the wireless tags, which would not require a scanner and could carry much more information.

A key element for implementation, however, is getting the price of the tags down to a few cents. Since pentacene can be spin-coated on thin, flexible substrates such as plastic film, it could turn out to be the route to very low-cost RFID technology.

The 3M researchers said they have achieved a breakthrough for organic RF circuits with a design that does not require external rectification to run the logic circuits. Rather than have a separate circuit to convert the incoming RF signal to dc, the gate and source areas of the organic transistors are overlapped to create a large-capacitance load that automatically filters out the RF component.

The result is a small circuit that will be cheaper to build, the 3M group said.

Pentacene also contributes to a more exotic application - electronic textiles - in a project at the University of California, Berkeley. Researchers in the department of electrical engineering and computer science have devised a process for building pentacene transistors directly on fibers using woven shadow masks.

While the viability of pentacene transistors on fibers has been demonstrated in the past, the processes used to define them were adapted from photolithography, which is not compatible with textile processes. The new technique could allow designs to be scaled up in existing textile factories to create true electronic textiles, the researchers said.

In another exotic application, arrays of pentacene organic transistors have been built into a flexible sheet to create a pressure-sensitive "skin" for robots at the Quantum Phase Electronics Center of the University of Tokyo. The sensor arrays are built layer by layer on polyimide films. The design could be realized with large-area printing technology to create low-cost, flexible membranes that could imbue robots with a sense of touch similar to that of the human hand, making them much more dextrous than in the past, the researchers said.

- Chappell Brown

EE Times

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