From the Labs: Information Technology

Bionic Eye
An electronic contact lens could act as an on-eye display or a biosensor.

Source: “Contact lens with integrated inorganic semiconductor devices”
Babak Parviz et al.
IEEE International Conference on Micro Electro Mechanical Systems, January 13-17, 2008, Tucson, AZ

Results: Researchers at the University of Washington have built a biocompatible contact lens with electronics and optoelectronics ­embedded in it. In preliminary studies in which the device was not turned on, a rabbit wearing it suffered no adverse effects.

Why it matters: A contact lens with both a wireless receiver and a display built into it could superimpose important information on objects in a soldier’s field of view. It could tell cell-phone users where incoming calls are coming from, and eventually it might even serve as a video screen. A lens with embedded sensors could detect critical biomarkers that indicate disease, giving doctors a noninvasive diagnostic tool and helping them track a patient’s health over time.

Methods: The lens was made from polyethylene tereph­thalate (the plastic used in beverage bottles), which was covered with metal wires in order to connect light-­emitting diodes. The researchers used chemicals to carve out circular indentations in which the LEDs would be placed. Because electronics are made at temperatures high enough to melt plastic, the LEDs were fabricated separately and transferred to the lens. The device was then coated with a biocompatible material and shaped.

Next steps: Right now, the LEDs are about 300 micro­meters in diameter, and no more than 16 working LEDs have been produced on a lens. LEDs this size tend to break during the lens-shaping process, so the researchers will try to shrink them to 30 micro­meters, which could make possible a lens display of a few hundred pixels. Also, the team needs to make sure that the electronic lens is safe for the eye when it is turned on.

Source: “Embedding cavities and waveguides in three-dimensional silicon photonic crystals”
Paul V. Braun et al.
Nature Photonics 2: 52-56

Results: Researchers at the University of Illinois, Urbana-Champaign, have developed a laser technique that can carve detailed, three-dimensional waveguides into silicon photonic crystals, materials with regularly spaced holes that can control the motion of photons.

Why it matters: Optical chips, which use photons instead of electrons to carry information, could speed up computers, because photons travel faster than electrons. They could also cheaply increase bandwidth in telecommunications equipment. Previously, researchers made flat, two-dimensional waveguides using lithography, a common chip-making technique. But a way to make three-­dimensional waveguides gives researchers more freedom in designing optical circuits: light can be bent around corners, and optical materials can be layered.

Methods: To build their photonic crystal, the researchers began by packing silica beads together to form a three-­dimensional matrix. They immersed the beads in a light-sensitive monomer, which flowed into the spaces between the beads. A precise laser beam solidified some of the monomer into “paths” of polymer. Then the researchers rinsed the structure, removing the excess monomer, and filled the remaining spaces between beads with silicon. Finally, they used an acid to dissolve the beads and the polymer, leaving a silicon structure with periodic holes where the beads had been and channels–waveguides–where the polymer paths had been.

Next steps: The researchers are creating waveguide designs that are more complex. They will also explore ways to build functional optical circuits.