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Optoelectronics/Displays??

Electronic contact lenses promise virtual display

Posted: 24 Jan 2008 ?? ?Print Version ?Bookmark and Share

Keywords:electronic contact lenses? LED? organic plastic?

Electronics contact lenses promise virtual display

Electronic contact lenses, made by depositing circuitry and LEDs on organic plastic, have been demonstrated by researchers at the University of Washington. The lenses promise to overlay a heads-up display over a user's visual field, enabling tactical informationlike an automobile speedometer for driversto be seen only by the wearer. So far the researchers have only completed animal testing on unpowered lenses, but for the upcoming human trials the researchers hope to power a virtual control panel that enables the display to appear to float in mid-air. Future applications could give military users virtual heads-up displays, give video gamers "anywhere" action, and let any contact-lens wearer surf the Internet sans monitor.

"Looking through a completed lens, you would see what the display is generating superimposed on the world outside, but there is much to be done before we have a fully functional display for human use," said EE Babak Parviz, a professor of electrical engineering at the University of Washington. "Our goal here was to demonstrate the basic technology, make sure it works and that it's safe."

Self-assembly
To fabricate the contact lens for testing on animals, the researchers had to solve the problem of how to deposit circuitry on the soft, flexible organic plastic substrates from which most contact lenses are made. To remedy this, Parviz designed a set of metallic circuit components, including custom LEDs that measured only one-third of a millimeter in diameter. The components were pre-assembled on a compatible organic substrate, complete with metallic contacts and a unique shape.

The contact lens' surface was then prepatterned with metallic traces to interconnect the components, along with cavities etched into the lens that matched the shapes of each component. The free-standing components were then mixed into a solution that was spread across the surface of the prepatterned contact lens and allowed to self-assemble on its surface. Each component's unique shape only allowed it to fit into a designated slot on the lens. Capillary forces similar to those that drive water upward against gravity in plants pulled each component into its assigned slot on the lens.

Vision issues
Although the LEDs were not activated in the animal trials, eventually a power source using integrated solar cells and a wireless RF receiver will enable the LEDs on the contact lenses to display information. The test lenses placed the LEDs in an array over the transparent part of the eye, while the supporting circuitry was kept around the edges where it would be out of the field of vision.

"The large area outside of the transparent part of the eye was used for placing instrumentation circuitry," said Parviz.

Eventually the lenses could also be used to correct a user's vision, and perhaps to even offer "zoom" and other capabilities by electronic activation of micro-lens functions. Parviz and his research group claim that despite the advanced functions they have in mind, all the necessary components are safe for use in the eye.

Besides Parviz, the other researchers include electrical engineer Harvey Ho, a former graduate student who is now working at Sandia National Laboratories. Other University of Washington EEs working on the electronic contact lens project included Ehsan Saeedi and Samuel Kim along with medical researcher Tueng Shen in the University of Washington's ophthalmology department.

This research was funded by the National Science Foundation and the University of Washington.

- R. Colin Johnson
EE Times




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