A contact lens that harvests radio waves to power an LED is paving the way for a new kind of display. The lens is a prototype of a device that could display information beamed from a mobile device.
Realising that display size is increasingly a constraint in mobile devices, Babak Parviz at the University of Washington, in Seattle, hit on the idea of projecting images into the eye from a contact lens.
One of the limitations of current head-up displays is their limited field of view. A contact lens display can have a much wider field of view. "Our hope is to create images that effectively float in front of the user perhaps 50 cm to 1 m away," says Parviz.
His research involves embedding nanoscale and microscale electronic devices in substrates like paper or plastic. He also wears contact lenses. "It was a matter of putting the two together," he says.
Fitting a contact lens with circuitry is challenging. The polymer cannot withstand the temperatures or chemicals used in large-scale microfabrication, Parviz explains. So, some components – the power-harvesting circuitry and the micro light-emitting diode – had to be made separately, encased in a biocompatible material and then placed into crevices carved into the lens.
One obvious problem is powering such a device. The circuitry requires 330 microwatts but doesn't need a battery. Instead, a loop antenna picks up power beamed from a nearby radio source. The team has tested the lens by fitting it to a rabbit.
Parviz says that future versions will be able to harvest power from a user's cell phone, perhaps as it beams information to the lens. They will also have more pixels and an array of microlenses to focus the image so that it appears suspended in front of the wearer's eyes.
Despite the limited space available, each component can be integrated into the lens without obscuring the wearer's view, the researchers claim. As to what kinds of images can be viewed on this screen, the possibilities seem endless. Examples include subtitles when conversing with a foreign-language speaker, directions in unfamiliar territory and captioned photographs. The lens could also serve as a head-up display for pilots or gamers.
Mark Billinghurst, director of the Human Interface Technology Laboratory, in Christchurch, New Zealand, is impressed with the work. "A contact lens that allows virtual graphics to be seamlessly overlaid on the real world could provide a compelling augmented reality experience," he says. This prototype is an important first step in that direction, though it may be years before the lens becomes commercially available, he adds.
The University of Washington team will present their prototype at the Biomedical Circuits and Systems (BioCas 2009) conference at Beijing later this month.
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