Biomedicine

Guiding Eye for MEMS

Researchers are developing a better scanner for Lasik eye surgery.

Problem: To make sure they target the right parts of the cornea during vision-correcting Lasik surgery, doctors rely on a scanner that responds to eye movements and redirects laser pulses. Today’s scanners cost thousands of dollars and still offer less than ideal precision.

Circular mirrors carved into silicon are controlled by motions of combshaped structures. (Courtesy of Hyuck Choo)

Solution: At the University of California, Berkeley, researchers in the Microfabrication Laboratory used inexpensive techniques to build a microscale scanner that moves up to 30,000 times per second, up from the 4,000 times per second of conventional technology. Graduate students Hyuck Choo and David Garmire invented a way to carve one piece of silicon into two interlocked comblike structures. Applying a voltage to one comb makes the other move up or down. A mirror attached to the combs redirects a laser beam. While “comb drives” are already used in some microelectromechanical systems (MEMS), the combs have had to be built on separate silicon wafers and wedged together manually. Because the new device is easy to manufacture, “this is not just an incremental step but a major development,” says Roger T. Howe, the Stanford University electrical engineer who invented the comb drive in the 1980s. Choo says the technology could be cheaply incorporated into surgical scanners and other devices.

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Biomedicine

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