Tech | July 03, 2008 | 35 comments

Sci-fi for the eyes

source: http://www.guardian.co.uk/technology/2008/jul/03/led.contact.lenses

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Babak Parviz wears contact lenses. But he's not yet using the new contact lenses he's made in his Seattle laboratory. Containing electronic circuits, they look like something from a science fiction movie. He's now going to add some extremely small light emitting diodes (LEDs), helping turn his prototype contact lenses into a sophisticated personal display - the tiniest one possible.

As an assistant professor of electrical engineering at the University of Washington, Parviz works on bio-nanotechnology, self-assembly, nanofabrication and micro-electro mechanical systems. He makes tiny but functional electronic devices and, using nanotechnology and microfabrication techniques, integrates them on to polymers or glass using a process known as self-assembly.

So how did he think of making a "bionic" contact lens? "Imagine a person with that kind of research expertise and background," says Parviz. "Imagine also the same person waking up every morning and putting a contact lens in his eye."

Looking ahead

Making the connection wasn't hard, as Parviz had also been thinking about unconventional displays. Contact lenses are made from flexible transparent polymers, just the sort of challenging material that Parviz likes to stick tiny electronic circuits on. "The driver is not to make something small. The driver is to make something that's cool and useful. Having a display in a contact lens is very useful."

Parviz argues that ironically, the current display sizes in mobile computers and phones hinder rather than help miniaturisation. "The display size is one of the main reasons that laptops, cellphones, PDAs, etc are not smaller today. If we move the display to a contact lens, we can significantly remove the physical constraints on mobile devices."

So far, he's shown that high-performance circuitry including microLEDs can be incorporated on to transparent, thin, flexible plastic substrates. The circuits involve making metal layers a few nanometres thick linked to LEDs that are about one third of a millimetre across. A microfabrication technique known as self-assembly relies on capillary effects to bring together pre-shaped pieces of circuit.

The prototype contact lens - which will eventually contain LEDs - has yet to be powered up. That key step, says Parviz, is several months off. "We're looking at two different ways to transmit power. One is radio frequency power transmission. We need antennae on these contact lenses anyway because we need to transmit data to them. The other way we're looking at right now is to incorporate photovoltaic [solar] cells."

Power isn't the hardest problem. A contact lens sits directly on the surface of the eye, much too close for the eye's lens to focus on. "To create the focused image we have to manipulate the light rays," says Parviz. "You can create a focused image if you use laser instead of LEDs."

If shining very low power diode lasers on to the retina seems risky, then microLEDs might be the answer. These provide diffuse light and, to make them work, Parviz might integrate an array of individual micro-lenses into the contact lens. "If the pixel [the microLED] is close enough to the micro-lens, it will generate a virtual image that could be 30cm or more away from the surface. Our eyes can focus on this now."

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