Terminator Vision: Check

Building a bionic eye

Peering into the future

Sep 30th 2009
From Economist.com

A contact lens that could put names to faces and guide soldiers in combat

University of Washington

SINCE the late 19th century, people with imperfect vision have been able to use contact lenses to improve their eyesight. In the early days these lenses were made of glass and could perform only simple visual corrections. Now they are usually made of plastic and can be moulded into the more complex shapes appropriate to those who suffer from astigmatism or who require bifocals. They can also be tinted, for people who wish to change the colour of their eyes. Yet the main purpose of even the most sophisticated contact lens remains what it always has been: to improve a person’s sight. That is about to change.

Researchers at the University of Washington, in Seattle, led by Babak Parviz, have incorporated electronic circuitry into a plastic lens, including light-emitting diodes (LEDs) for “on-eye” displays, transistors for computing, a radio for wireless communication and an antenna for collecting power from a radio source, such as a mobile phone, in a person’s pocket.

Making a “smart” lens like this is not easy. Electronic components are usually manufactured at temperatures which would melt plastic and are made of materials that do not naturally adhere to a contact lens’s plastic. Dr Parviz and his colleagues have therefore designed a lens that is peppered with small wells, ten microns deep, that are connected by a network of tiny metal wires. Each well is sculpted so that a component of a particular shape will fit snugly into it and, at its bottom, it contains a small amount of an alloy with a low melting-point. In addition, wells that will accommodate LEDs must be fitted with microlenses to focus the light from the LED in a way that the eye can cope with.

The components are manufactured individually and suspended in a liquid. This suspension is then washed over the lens, allowing the components to blunder into holes of the appropriate shape, where they stay put. The alloy is then gently heated, melting the alloy and connecting the components to the wires and thus to one another.

The researchers say that the resulting circuitry requires so little power that it does not produce enough heat to cause discomfort. And although Dr Parviz has not, himself, worn the lens, he has tested it on rabbits—and the animals do not seem to find it uncomfortable.

So far, the prototype’s display is rudimentary (in truth, it consists of but a single LED). However, Dr Parviz and his colleagues are working on a lens that can accommodate an eight-by-eight array of LEDs. They are also exploring a design which produces images using tiny shutters, in the manner of a liquid-crystal display.

As well as an LED, the prototype contains a small radio chip and antenna so that it can be powered without wires. The researchers will discuss the performance of their wireless-power system, which taps into the mobile-phone frequencies in the range 900-megahertz to 6-gigahertz range and draws about 100 microwatts of power, at a conference in Beijing in November.

What the display will show, of course, is up to the imagination—the name, perhaps, of someone the wearer has met but does not recall, or the street directions in an unfamiliar city. Or, perhaps, the quickest route to a target that needs destroying. For this sort of technology surely has military applications as well.

http://www.economist.com/sciencetechnology/tm/displayStory.cfm?story_id=14538587