Then they took a piece of elastic rubber, stretched it, and stuck the silicon strips to it.
When the researchers relaxed the strain on the rubber, it returned to its original size. Each silicon strip, stuck to its shrinking foundation, buckled into a wavy, accordion-like shape.
The waves in the silicon's structure were less than 50 micrometers (0.002 inch) long.
When the researchers subsequently stretched or compressed the rubber-and-silicon pieces, the wavelength in the silicon strips expanded or contracted accordingly, without breaking.
Rogers and his colleagues describe their engineering methods and follow-up testing on the wavy circuits in tomorrow's issue of the journal Science.
The team has done "very nice work," said Wagner. "It's a step toward any kind of flexible electronics."
Takao Someya of the University of Tokyo's School of Engineering called the advance "one of the major breakthroughs" needed for creating "wearable electronics and/or integration of electronics with biological tissues."
Applications and Obstacles
Wagner said that, by sculpting circuits, "you can build a spherical lens, like an eye." That could shrink systems of optical sensors to barely a tenth of their current sizes, he said.
"It would be a revolution in digital cameras," he added.
The Princeton engineer also imagines artificial limbs with surface sensors that deliver electrical impulses to severed nerves. And, he said, latex gloves studded with sensors could put information about a patient's vital signs literally at the fingertips of an operating surgeon.
Rogers envisions aircraft wings that sense their own structural health.
But Wagner says the team's invention falls short of what's necessary for those futuristic uses.
Circuits have to be manufactured in flat sheets, Wagner notes. So to assume complex shapes, such as that of a partial sphere, circuits would need to be what he calls fully deformable.
The new circuitry may be bendable and stretchable, but it's not deformable, Wagner says. "It's not going from flat to a sphere."
Electronics makers such as Samsung and Philips are nevertheless working on flexible electronics.
Initially, experts say, advances are only likely to yield improvements in existing devices, for example by making them more rugged.
The conventional, rigid components in liquid-crystal displays (LCDs)used in Apple's new video iPods as well as many TVs and computer monitorsare easily broken, Wagner notes.
If iPod video monitors and their like are someday made with bendable components, though, "the screens won't break anymore," he added.
"Flexible displays appear to be the first application likely to be commercialized," Rogers agreed. "You might see these devices in PDAs and so in the next year or two."
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