Berkeley researchers develop flexible touch screen

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Nathaniel Solley/Staff

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Imagine living in a world where paper-thin computer screens cover walls instead of paint. They would respond to your very presence in a room, attuned to and controllable by your every movement — even your facial expressions.

Engineers at UC Berkeley and Lawrence Berkeley National Laboratory have taken the latest step toward that by developing a thin, pliable plastic material called “e-skin” that is interactive like a touch screen but more flexible than the rigid glass or silicon currently used in smartphones and computers.

The team of researchers, led by UC Berkeley professor of electrical engineering and computer sciences Ali Javey, created a working stamp-sized prototype that responds to touch by emitting light. The work was published in the academic journal Nature Materials on Sunday.

E-skin is not a synthetic replacement for human skin, despite what the name may suggest, Javey said. E-skin will primarily be used in electronics and aims only to mimic human skin in computer displays by responding similarly to touch, temperature and light.

“From the engineering point of view, human skin is an interface that provides us with information,” Javey said.

When pressure is applied to e-skin, its surface lights up with organic light-emitting diodes, an advanced form of LEDs. The intensity of the light varies with the intensity of pressure exerted on the skin, said Chuan Wang, a professor at Michigan State University who co-authored the publication and worked on the research as a UC Berkeley postgraduate.

According to Wang, prior to using OLEDs, the only way to measure the pressure being applied to a surface was to measure electrical currents, which required extensive equipment. Integrating light sensors into e-skin has simplified the process of detecting pressure by eliminating the need for electrical boards or a computer.

The researchers are now working to have e-skin respond to light and temperature as well.

But there are still significant challenges to overcome before the use of plastic as a platform for electrical systems can advance.

“Existing equipment is designed to only process rigid substrates, like silicon,” Javey said. “For plastic substrates, we have to develop new equipment in order to build complex electrical structures.”

Researchers believe e-skin could be used in large-scale applications in the future. It may ultimately be possible to cheaply print e-skin on regular printers using metallic ink and thin plastic.

Dae-Hyeong Kim, a professor of bioengineering at Seoul National University who does research on similar materials to e-skin, said Javey’s material is significant because it reacts by emitting light — a more natural way of interacting with humans than traditional electronic sensors.

“The recent work from Professor Javey’s group has a great meaning in that it realized the interactive mode of artificial electronic skin,” he said.

Contact Stephanie Petrillo at [email protected]

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