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A Tiny Robotic Hand

An ultrasmall grabbing gadget might someday become a new tool in microsurgery.
January 26, 2007

Early this winter in a University of California, Los Angeles (UCLA), laboratory, a mechanical hand less than one millimeter wide deftly plucked a single fish egg from a gooey underwater clutch, demonstrating a new technology that could one day make it into surgeons’ tool kits.

A new feat of microscale mechanical systems, or MEMS, this tiny “hand” developed by researchers at the University of California, in Los Angeles, is operated with gas pressure so that it can function in wet or dry environments. In the video, the hand detaches a one-millimeter-in-diameter fish egg, overcoming the surface tension that is strong at this scale. It does so gently enough not to crush the egg. No such MEMS device exists today.

“It is the world’s smallest robotic hand, and [it] could be used to perform microsurgery,” says Chang-Jin Kim, the lead researcher at UCLA, who says the device is safe for biological applications. Since it runs on gas pressure instead of electricity, it can be used in both dry and wet environments.

The “microhand” measures one millimeter across when closed into a fist. It consists of four “fingers,” each of which is made from six silicon wafers, with polymer balloons doing the work of “muscles” at the wafers’ joints.

Each balloon is connected with narrow channels through which air is pumped in or out. When a balloon is inflated, the distance between two joints decreases, and the finger flexes inward. Upon deflation, the fingers relax. And with selective inflation and deflation, researchers are able to manipulate the fingers into clasping or releasing an object.


  • Watch the hand detach a fish egg

“I must say that the microhand is a wonderful [micro-mechanical] achievement,” says Albert Pisano, a mechanical engineer at the University of California, Berkeley, and a leader in such research. “The field of microsurgery and minimally invasive surgery is currently dominated by grippers and tools that are mounted at the end of long, rigid aluminum rods. Certainly these are adequate for many purposes, but now that functional microhands have been developed, one can visualize a new set of minimally invasive surgical tools that allow the surgeon additional dexterity in complicated procedures.”

Pisano says that the technology could enable new kinds of minimally invasive surgical techniques, and that it stands out from other such efforts. “The work of Professor Kim is especially noteworthy since he has two pairs of opposing finger/thumb sets and … his design is able to have such an extreme range of motion.”

While the microhand is probably years from practical use, the UCLA researchers say they are currently working with a firm involved with remote surgery to develop a slightly bigger hand, which will incorporate optical fibers on the palm. The idea, Kim says, is to have a microhand with an “eye.” This could be used for seeing and manipulating objects within the human body.

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