A team of researchers led by Babak Amir Parviz, an associate professor
of electrical engineering at the University of Washington, just
published a paper in the 22 November edition of the Journal of Micromechanics and Microengineering
that described a breakthrough in the development of an electronic
contact lens with a built-in display. Parviz, who collaborated with
University of Washington ophthalmologist Tueng Shen and optoelectronics
researchers from Aalto University in Finland, has for several years been
working on contact lenses that will someday augment the wearer’s vision with external data or use sensors to collect data about the state of the wearer’s health.
The researchers say that they successfully created a single-pixel
wireless display comprising a blue gallium nitride LED mounted on a
transparent sapphire chip, an integrated circuit that doubles as a power
harvester and controller for the LED, and metal interconnects. They
also showed that a series of passive lenses (called Fresnel lenses) less
than 1 micrometer thick, when placed on the surface of the contact lens
about 360 micrometers away from the LED, can focus the LED light onto
the retina in a way that makes it appear as though the single-pixel
image is floating in space about 1 meter away from the eye. Otherwise,
the image would be right up against the cornea, where the human eye is
incapable of bringing objects into focus.
Of the high-tech miniature display, the researchers said that although
it has only one controllable pixel, “…we have provided the first
proof-of-concept technology demonstrations for producing multipixel and
in-focus images using a contact lens by producing multipixel micro-LED
array chips on transparent substrates and micrometer-scale Fresnel
lenses that can be integrated into a contact lens.” In other words, the
team is making significant progress toward the goal—an array of 3600
10-µm-wide pixels spaced 10 µm apart—that Parviz mentioned in the
September 2009 IEEE Spectrum article “Augmented Reality in a Contact Lens.”
Now that the researchers have demonstrated the ability to remotely
control red and blue LEDs, doing so with green ones is the next step in
order to produce full-color displays integrated into contact lenses.
Among the technical hurdles that remain is developing an improved power
supply. The 5-millimeter-radius loop antenna used to draw power
wirelessly in the experiments documented in the paper only harvests
enough energy when it is within about 2 centimeters of the radio
transmitter. Another problem is that the so-called bionic lens is made
from polyethylene terephthalate, a form plastic that is not porous
enough to be worn against the eye all day. Its poor oxygen permeability
could lead to corneal swelling. But the team says it is already back in
the lab, attempting to overcome these challenges
Source:http://spectrum.ieee.org/tech-talk/biomedical/bionics/wireless-display-on-a-contact-lens
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