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Scanning Vol. 24, 5 (2002) 271 Scanning the Industry The Future in Sight

Six individuals never thought they would regain their sight. But an experimental microscopic silicon chip artificial retina (ASR™) developed by Optobionics offers some possibility of renewed vision.

The ASR microchip functions with a retina that has partial outer retinal degeneration, so the remaining cellular layers must still be intact. The chip is then implanted in a small slit behind the functioning cells in the damaged retinas. All six participants implanted to date in the Optobionics clinical trial report they have regained some measure of eyesight.

These preliminary results are gratifying to ASR microchip creators Vincent Chow, an electrical engineer, and his brother Alan Chow, a pediatric ophthalmologist, who founded Optobionics in 2000.

Vincent and Alan used the JEOL 35C and 840 microscopes to research, develop, and manufacture the ASR chips. They designed the microstructure that fits in the sub-retinal space in 1988, when Alan suggested there may be a way to surgically and clinically generate electrical impulses that could stimulate sight. Working with a scanning electron microscope (SEM) at the microstructure and low-voltage levels, they were able to see immediate results indicating either progress or the need for a revised “recipe.”

Under FDA guidelines, they used the standard SEM for all surface and visual examinations during the manufacture of the ASR microchip. “If the surface is contaminated, the SEM can see it but it would be invisible under the optical scope. We use the FDA guidelines as part of the standard manufacturing process of our implants,” Vincent said.

“We’re developing innovative programs using the JEOL microscopes to look at the surface electrical functionality without touching the surface. We have microscopic solar cells populating the surface of our implant, so normally we have to physically touch it with some kind of electrode needle in order to observe the electrical properties. Under voltage contrast mode, it’s possible to see these electrical activities using the beam without ever touching the sample,” he added.

Performance assessment is another area Vincent and Alan have studied with the SEM. “If you had a chip and you had to trace the connector between two transistors and it began to wiggle, the SEM can actually tell you at what voltage level it’s occurring, so the grey scales from the SEM under voltage contrast can be made proportional to the voltage that’s actually on the conductor. We use this to assess the implant performance. Because we have so many cells on the surface (in excess of 4,500), this type of scanning is extremely effective compared to mechanical probing techniques.”

Today, Optobionics produces controlled etching features within its ASR microchips. “The implants are only 25 microns in thickness, and we have to sculpt different features into the surface to make it compatible with the eye. We use the SEM to guide us in what recipes should be used to produce what kinds of contours on the surface. This is done through reactive ion etching. Without the SEM, we couldn’t see the immediate benefits of the recipe or the modification,” he noted.

The JEOL microscopes have played and influential role in the development of ASR microchip technology. The backbone of JEOL Ltd. at its founding in 1949 was electron optic technology and, as evidenced by the work of Optobionics, it remains so today. JEOL produces 12 models of microscopes ranging from its flagship transmission electron microscope (TEM) to the scanning electron microscope (SEM) and scanning probe microscope (SPM). Vincent credits JEOL for consistently strong service and support of its microscopes, and has recently purchased the company’s 6460LV model.

Manufacturers are regularly called upon to meet the demands of changing markets and technology and to increase product capabilities. JEOL product manager Charles Nielsen comments, “Ultimately the solution is a function of the quality of the electron optics. Over the years, JEOL has developed techniques and a basic understanding of how to improve or reduce the aberrations in the magnetic fields that are the lenses. It’s a matter of refining not only the manufacturing process but certainly the development of the lenses themselves,” For Vincent, the ability to image at low voltage is a primary requirement of a SEM, allowing him to minimize the possibility of altering the surface properties of the ASR implant.

Through the application of technology, software, and hardware developed by leading industry manufacturers, companies such as Optobionics are performing previously unattainable feats–such as bringing vision to the blind. For Vincent, this achievement is the most gratifying and rewarding part of his work. And the future looks even brighter: “Optobionics envisions a future where the ASR microchip technology will call upon every area of science to improve its potential performance. We envision using micromachining, nanotechnology, and many of the miniaturization techniques and optics being developed for display technologies today.”