Meanwhile, other researchers are adapting the microelectrode technology specifically for retinal implants. Orlando Auciello and his colleagues at Argonne National Lab are working on making silicon microchips bio-inert by incorporating carbon, albeit in another form--a material they have developed called ultrananocrystalline diamond. While silicon cannot be placed directly in the eye, a chip encapsulated with this material could be, Auciello says. The device is now in clinical trials. Since the diamond-coating technology has not been fully developed yet, each of the six patients in the clinical trial had a microchip implanted on the side of the head that is connected to a platinum electrode array in the retina. The electrodes are 500 micrometers in diameter.

With the smaller carbon nanotube electrodes, Auciello says, "You can address much lower number of cells with one electrode, even if it doesn't go to a single cell." The Stanford work opens up the possibility of integrating carbon nanotubes on the silicon microchip, he says. "This new development is very exciting if it can be reproduced."