The trick, Parviz said, was to place most of the minute components in the areas over the eye's natural blind spots.
Perhaps the more pressing problem was how to attach the electronic components—each thinner than a human hair—to the delicate polymer of a contact lens.
Direct placement would probably damage the lens and be too time consuming.
Instead the team built separate, nano-size metal components and mixed them together so that they appeared like a fine powder.
This powder was then placed in a vial of fluid and poured over a pitted lens surface.
Each pit corresponded to a particular component, so as the mixture washed over the lens, the components found their positions.
A molecular adhesive force known as capillary action—the same property that allows plants to "suck up" water—locked the pieces into place.
The lenses were then put into the eyes of lab rabbits, which showed no signs of adverse effects after at least 20 minutes of wear.
Parviz's team has not yet activated the lens' circuitry; the goal of the new research was to show how such a device could be built and safely worn.
He admits that more research needs to be done in terms of understanding how the human eye would focus on the information.
"It will be difficult to see an image that will be formulated directly on the lens, so we will have to manipulate light so that it appears that the image is further away," he said.
If commercialized, the first generation of lenses would likely have low-resolution displays that probably could not convey much information.
But as the technology improves, the possibilities would be seemingly unlimited, the researchers said.
Drivers could read directions without taking their eyes from the road. Mechanics could get diagrams overlaid onto their equipment as they work. And virtual gamers could use the real world as a backdrop for their adventures.
(Related news: "Mobile Games Superimpose Virtual Fun on the Real World" [October 16, 2006].)
At Georgia Tech, MacIntyre's lab recently assembled a prototype virtual tour of the historic Oakland Cemetery in Atlanta.
As visitors move about the grounds, they hear voice actors tell the stories of cemetery residents through a special headset and handheld controller.
Replacing such devices with enhanced contact lenses would be easy, MacIntyre said, and the public would readily adopt such lenses if they were useful and unobtrusive.
After all, he noted, people are already becoming acclimatized to a variety of mechanical enhancements.
"I never would have imagined five years ago," he said, "that so many people would be wearing those little Bluetooth headsets."
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