Joined: 16 Mar 2004
|Posted: Tue Aug 11, 2009 10:50 am Post subject: More than Meets the Eye – The LED Contact Lens
|Prototype contact lenses that include LEDs and circuits could become a tiny personal display
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.
A researcher holds one of the completed contact lenses
Image credit: The Guardian
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."
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."
All this raises questions of biocompatibility: the electronics in the contact lenses must not harm the eye. If that's assured, then the idea of a fully functional wireless display on a contact lens might seem, at first, to have many uses.
Parviz talks about augmented reality, such as superimposing text messages or direction arrows on your view of the world. But even trivial applications will require a high-resolution display. So his next step is to demonstrate a programmable wireless contact lens with a few pixels - perhaps eight - that's safe to wear. Since his work became widely known, Parviz has received emails from people wanting to test the contact lenses, while others have proposed ideas. He's also had emails from those with vision problems, an area he hopes to help with.
An 11-year-old student also wrote in describing a school competition involving an idea for a "closed caption eye" using electronic contact lenses for the hearing-impaired. For example, a fire alarm symbol appears when the alarm sounds, an idea Parviz now has in mind. "We are looking right now at gaming, augmented reality, computing, telecom and medical applications."
However, Professor James Wolffsohn of Aston University in Birmingham isn't enthusiastic. As the head of optometry, his research interests include contact lenses. "I've never seen anyone try and print circuits on to a contact lens," says Wolffsohn.
He points out that a contact lens is around 14mm wide, compared to the pupil's diameter of between 4mm and 5mm. He reckons that doesn't leave a lot of space for electronics without interrupting vision; and it might be difficult to project an image from the periphery into the eye's central area.
"The focusing would be the real issue. These are incredibly close to the eye," says Wolffsohn of Parviz's plan. He adds that while dust in a contact lens is uncomfortable, you don't see it because it's just too close. The same applies to images on the contact lens. "There would have to be some projection technology for it to appear at a distance that you could then focus on. I can't really see them generating a projection through a contact lens."
Wolffsohn also doesn't think the research will help low-vision sufferers who need high-contrast large-text solutions; only a very small number wear contact lenses already. Most people commonly needing vision correction choose glasses, and, as for laser diodes: "There would certainly be issues about laser damage to the retina."
Nevertheless, Wolffsohn is attracted to the idea of putting electronics on to glasses (as has been done with some products already). There's more space and no biocompatibility issues, while image projection is an easier proposition. His verdict on using contact lenses as a display device? "They wouldn't be my starting point if I had this technology," says Wolffsohn. But whichever way this research goes, it's worth keeping an eye on
Source: Michael Pollitt - http://www.guardian.co.uk/technology/2008/jul/03/led.contact.lenses