Seeing The LightSeeing The Light

A ceramic microchip inspired in part by semiconductor design could one day help restore sight to some fully and partially sightless people. It could replace the millions of rods and cones in the back of the eye that collect light and transmit it along the optic nerve to the brain. When rods and cones don't function properly, blindness can ensue.

NASA scientists at the Space Vacuum Epitaxy Center in Houston have come up with a thin-film ceramic microchip so fine that surgeons can't handle it, but if implanted in the eye, the microchip could replace defective rods and cones.

Space exploration and semiconductor technologies led to the discovery. The Wake Shield Facility, a 12-foot disk platform launched from the space shuttle, allowed engineers to study epitaxial film growth in the vacuum of space. Because the detectors--the individual units that detect light in much the same way as do natural rods and cones--closely resemble the ultrathin films used in the chips, the engineers can use their semiconductor expertise and make the detectors in arrays, like chips in a computer factory, says Alex Ignatiev, a physics professor at the University of Houston.

Researchers create the film through epitaxy: building it up atom by atom and layer by layer on a background substrate of platinum film. Then each film is stacked hexagonally, just as natural rods and cones are.

Put 100,000 of the minute ceramic detectors together, in an array style similar to that of semiconductor chips, and scientists can create an ceramic thin-film microdetector. At 5 microns (a fraction of the width of a human hair), it's too small for surgeons to handle safely. So the chip would be attached to a temporary polymer film, 1 millimeter by 1 millimeter. Within a couple of weeks of the implant, the supporting polymer would dissolve, leaving only the ceramic thin film to function as rods and cones.

The first human trials are set to begin this year.