Blind World

MEMS Chip Could See for the Blind.

October 2, 2002.

By Peter Singer ,
Semiconductor International.

Enabling the blind to see -- a task once thought the province of miracles -- is the goal of a technical team that includes Sandia National Laboratories (Albuquerque, N.M.), four other national labs, a private company, and two universities.

The lead lab, Oak Ridge National Laboratory (Oak Ridge, Tenn.), will manage the multi-laboratory effort as well as test the various components developed by the other labs.

Argonne National Laboratory (Argonne, Ill.) will investigate the viability of diamond-based electrode arrays and biocompatible coatings; Lawrence Livermore National Laboratory (Livermore, Calif.) will experiment with rubberized electrode arrays; and Los Alamos National Laboratory (Los Alamos, N.M.) will model and simulate neural paths of and from the retina to the brain.

Personnel from the University of Southern California (Los Angeles) will implant the devices and test their medical effectiveness.

Second Sight (Santa Clarita, Calif.), will commercially produce the finished system.

North Carolina State University (Raleigh, N.C.) leads the development of the in situ medical electronics.

The idea, funded by a $9M, three-year grant from the Department of Energy's (DOE) Office of Biological and Environmental Research (BER) in Washington, is to create 1000 points of light through 1000 tiny MEMS (microelectromechanical systems) electrodes.

The electrodes will be positioned on the retinas of those blinded by diseases such as age-related macular degeneration and retinitis pigmentosa.

These diseases damage rods and cones in the eye that normally convert light to electrical impulses, but leave intact the neural paths to the brain that transport electrical signals. Eventually the input from rods and cones ceases, but 70-90% of nerve structures set up to receive those inputs remain intact.

"The aim is to bring a blind person to the point where he or she can read, move around objects in the house, and do basic household chores," said Sandia project leader Kurt Wessendorf. "They won't be able to drive cars, at least in the near future, because instead of millions of pixels they'll see approximately a thousand. The images will come a little slowly and appear yellow. But people who are blind will see."

The plan is to use a tiny camera and radio-frequency transmitter lodged in the frame of a patient's glasses to transmit information and power to modules placed within the eyeball. The modules will be linked to retinal nerves that will send electrical impulses to the brain for processing.

"We felt that blindness is a devastating problem and that the modern conjunction of materials science with micro- and nanotechnologies in our multidisciplinary national labs offers possibilities for advances where before people had hit brick walls," said Dean Cole, a biomedical engineer who directs the project at BER. The Sandia approach is to attach a MEMS chip on the retina -- that is, within the vitreous humor of the eyeball -- made of LIGA and surface micromachined silicon parts. (LIGA, a German acronym for lithography, electroplating and molding, makes small parts of metal, plastic, or ceramics.) The idea is to directly stimulate some of the nerve endings within the retina to produce images good enough to read large print and distinguish between objects in a room.

"Compared to the elegance of the original biological design, what we're doing is extremely crude," Wessendorf said. "We are trying to build retinal implants in the form of electrode arrays that sit on the retina and stimulate the nerves that the eye's rods and cones formerly served."

The size of cones and rods, as well as nerve connections, are in the micron range -- a difficult but doable realm for scientists used to working with micromachines.

"We'll use a crude, shotgun approach that fires groups of nerves. In the long run, of course, we'd like to stimulate each individual nerve," said Sandia manager Mike Daily.

Goals of the project increase from 10 10 electrode arrays for fiscal year 2002 to 33 33 arrays for fiscal year 2004.

"Integrating microdevices into the human eye is incredibly challenging because of the need for high-reliability operation over decades in a saline environment," Daily said. "BioMEMS interfaces and biocompatibility issues drive much of the effort, particularly in the packaging of the microsystem." Packaging refers to sealing and securing a microdevice in place and linking it electronically and physically with its environment.

Counterintuitively, the rods and cones of the retina lie beneath nerves, not above them, which makes it slightly easier to connect directly to the nerves.

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