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Posted: June 3, 2008
Artificial arm operated by power of thought
(Nanowerk News) Prostheses that can be moved as easily as a sound hand only exist in science fiction movies – or at least that has been the case up to now. Researchers are working on a miniaturized neural interface capable of intercepting nerve signals and forwarding them directly to a prosthesis.
The minuscule object, resembling a tiny square sequin with a hundred fine sharp needles projecting from its surface and measuring no more than eight millimeters on each side, doesn’t look particularly remarkable at first glance, and yet in a few years’ time this Integrated Neural Interface could be helping amputees to move a prosthesis almost as efficiently as a sound hand or leg.
The electronic device serves as an interface connecting the nerves in the damaged extremity with the prosthesis by intercepting the signals emitted by the nerves and forwarding them to the prosthesis. The prosthesis interprets these signals and translates them into physical movements.
The research team devoting its efforts to realizing this vision is made up of scientists from the Fraunhofer Institute for Reliability and Microintegration IZM in Berlin and the University of Utah in the United States.
The American researchers made the first medical breakthrough in 2004, when they implanted the needle array in the motor cortex of a 24-year-old paraplegic patient. After a short period of special training, the young man was able to move his artificial arm exclusively through the power of his thoughts. At that stage, the electronic interface was basically fully functional but simply too big to be implemented as an integrated implantable device. The interpretation of the signals by the microprocessor had to take place in an external device. The needle array and the processor were linked by wires that passed through the cranium. These wires terminated in a dual-function connector on the patient’s scalp, which allowed the interface to be supplied with power and permitting data to be read out of the microprocessor. The task assigned to the IZM team was to reliably integrate the various components of the sensor in a single miniaturized unit with a surface area of less than one square centimeter.
The new advance overcomes one of the major obstacles standing in the way of practical implementation of the neural interface: It requires no external wiring. A coil supplies power to the interface by induction, permitting it to operate without batteries. “The development of this coil has enabled us to produce the world’s first wireless neural interface capable of detecting nerve signals directly, without any intermediate device,” says Matthias Klein, research physicist at the IZM. Once it has been implanted, the artificial interface must remain in place for up to several decades. “Naturally, to ensure that the system is not rejected by the patient’s immune system, we do not use any allergenic materials such as nickel, copper, silver or lead,” Klein adds.