Scientists Develop Touch in Prosthetics

TouchResearchers have made significant advances in recent years in developing and building better prosthetics from legs that enable an amputee to walk to arms and hands controlled by the brain.

But a Chicago researcher working on a project funded by the Defense Advance Research Projects Agency says it’s not enough for the brain to send a signal to a limb. It’s important for the brain to get a signal back to restore a sense of touch.

“To restore sensory motor function of an arm, you not only have to replace the motor signals that the brain sends to the arm to move it around, but you also have to replace the sensory signals that the arm sends back to the brain,” Sliman Bensmaia, an assistant professor in the university’s Department of Organismal Biology and Anatomy, said in October, when the research was published in the Proceedings of the National Academy of Sciences.

“We think the key is to invoke what we know about how the brain of the intact organism processes sensory information, and then try to reproduce these patterns of neural activity through stimulation of the brain,” he said.

Bensmaia’s work with DARPA, if successful, is a big step in developing a prosthetic that a fully functional artificial limb, since the wearer would not only have the ability to  pick up objects with the ease of thought – say a hammer or an egg – but would feel the difference.

In the lab, the researchers have already had some success using monkeys, and have been cleared for human trials. The work requires electrodes be implanted in the brain.

What they have done is linked artificial fingertips to the brains of rhesus monkeys trained to signal when they feel contact or pressure to their own real fingertips. Once parts of the brain responsible for receiving and interpreting signals for a range of sensations, including heat, cold, weight, etc., are identified, they would be linked to a prosthetic that incorporates sensors that in real time instantly transmits this data to the brain.

Once perfected, the wearer would feel the object in the same way he would with a human hand.

In July, DefenseTech reported on work at the University of Tokyo that could lead to an artificial skin that would provide a sense of touch or feeling to wearers of prostheses.

In that project, engineer Martin Kaltenbrunner is developing an ultra-thin, featherweight electronic sensor foil that can be shaped or molded to any surface.

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