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A most versatile metal foil

Stainless steel and the benefits of flexible displays

Fold up your laptop. Put down your PDA. Be careful – their state-of-the-art display is encased in a glass substrate that might break if you make a hasty move. But what if your profession or pastime doesn’t let you pamper your electronic gadgets?

What if you’re a soldier tracking terrorists or a jogger monitoring blood pressure? Or an engineer fitting a space shuttle with sensors?

Is it too much to ask for electronics that conform to your needs instead of requiring you to conform to theirs?

Not at all, says Miltos Hatalis, professor of electrical and computer engineering and pioneer in the field of flexible displays.

Hatalis concedes that glass-substrate technology has had its benefits, giving us PDAs and laptops, as well as PCs, high-definition TVs and other devices with images generated typically by liquid-crystal displays (LCDs).

But after fabricating electronics on glass for 15 years, Hatalis began in the late 1990s to pursue flexible displays on metal foils.

Now he is seeking to mount your big-screen HDTV on a flexible metal-foil substrate that can be rolled up and stored in a tube when it is not being used. He believes soldiers and rescue workers will soon scout unfamiliar terrain with interactive electronic maps displayed on flexible displays mounted on their uniforms.

And he envisions the day when paper-thin sheets of sensors, wrapped “conformally” around the fuselage and wings of an aircraft, give engineers a more complete picture of fatigue cracks as they develop.

Hatalis and his group in Lehigh’s Display Research Laboratory have moved to the forefront of metal-foil research. In 1999, they demonstrated the first transistors on metal foils, and in 2003, they fabricated the first high-performance circuits on foils. In 2006, they placed a 3.3-inch diagonal display of 330,000 pixels, each containing two transistors, on a 6-inch stainless-steel wafer. The group has received funding from DARPA, the U.S. Display Consortium, the Army Research Laboratory and Lehigh’s Center for Optical Technologies. It enjoys logistical and financial support from Lehigh’s Sherman Fairchild Center for Solid State Studies.

Beyond the OLED wave
As the electronics world prepares to advance from LCD to OLED (organic light-emitting diode) technology, Hatalis is looking farther into the future.

This year, Sony plans to introduce the first OLED TV. In two years, analysts predict, the market for the new TVs could exceed $1 billion. The market for all OLED displays – signs, TVs, computers, laptops and handheld devices – is expected to approach $11 billion by 2012.

OLED displays, whose thin organic films emit light when an electrical current flows through them, promise one day to be thinner, less power-hungry, simpler and cheaper to manufacture than LCD displays. Both technologies rely on thin-film transistors and both, for the time being, are housed on glass substrates.

This is where Hatalis’s group comes in.

“We believe we are one step ahead,” says Hatalis. “We’re taking the thin-film transistor (TFT) technology that enables big-screen TVs, cell phones, MP3s, etc., and we’re importing it from glass onto flexible substrates.

“Flexible displays are thinner, lighter and more conformal than glass displays. Glass can be used only for flat rigid displays. Flexible displays are virtually unbreakable. They can be folded or held like a newspaper. And flexible OLED displays consume less power than LCD displays.”

Flexible display researchers form two camps, says Hatalis – those who work with plastic substrates and those who work with metal foils.

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Miltos Hatalis envisions the day when TVs, computers and other electronic displays move from glass substrates to thin, flexible metal foils that can conform more readily to the needs of the 21st century.
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