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13 February 2002

Artificial hand becoming more human

Advances in human-to-machine communication and miniaturization could bring the technology of artificial limbs working like the real thing close within a decade.

That is what Rutgers biomedical engineer and inventor William Craelius said. He created the Dextra artificial hand, which allows a person to use existing nerve pathways to control individual computer-driven mechanical fingers.

"Bionic technologies can be adapted for restoring some degree of almost any lost function," Craelius said. He added that if progress continues at its present pace, "human-machine communication could soon lose its distinction as the No. 1 obstacle to bionics."

As an example, he described a wireless implant the size of a grain of rice, developed at UCLA by a team led by Dr. Gerald Loeb. Doctors inject the device under the skin to provide independent communication between nerves and bionic devices. Craelius said while it may require more than 1,000 connections between the brain and bionic devices to communicate the data for a complex action such as walking, it is probably achievable, even if most of the necessary computer processing is done outside the body.

Miniaturization of components will eventually bring that processing inside the body, Craelius said. "The number of transistors we can fit onto an integrated circuit doubles about every 18 months," he said. "At this pace, within the decade the processing for complex bionic activity will be implantable in the brain or elsewhere in the body."

While scientists are eliminating obstacles to communication and miniaturization of bionics, they still need to devise ways to protect the tiny devices from electromagnetic interference and corrosion from bodily fluids, Craelius said. Battery capacity and recharging are also concerns as the devices handle an increasing number of tasks.

"Finally, users who subject themselves to brain implantation of hundreds of electrodes are not going to want bulky plastic sockets for their new bionic limbs," he said. "Creating a more natural integration between the limb and existing bone is going to be vitally important. A human feel is a crucial part of bionic restoration."

Human feel is an area Craelius is addressing in his own work with Dextra, an artificial hand he developed along with a team of Rutgers students and Nian-Crae, Inc. The prosthesis gives a person who has lost a hand natural control of up to five independent artificial fingers. Controlled by electrical signals generated by the user's remaining muscles and tendons, Dextra allows such complex hand activities as typing and piano playing. It has a plastic socket that encases an amputee's upper limb. A device worn outside the body handles some of the processing and communication.