Bionic Arms
Here's a link to an article in the Washington Post about a woman receiving a bionic arm. It's mind-blowing, and here's an excerpt:Mitchell, who lives in Ellicott City, is the fourth person -- and first woman -- to receive a "bionic" arm, which allows her to control parts of the device by her thoughts alone. The device, designed by physicians and engineers at the Rehabilitation Institute of Chicago, works by detecting the movements of a chest muscle that has been rewired to the stumps of nerves that once went to her now-missing limb.
...All she has to do [to peel a banana] is place her prosthetic left arm next to the banana and think about grabbing it. The mechanical hand closes around the fruit and she's ready to peel.
Here's an excerpt about how it's done:
In preparation for the bionic arm, Kuiken and his surgical colleagues first re-create a biological control panel for a hand on the amputee's chest. They use muscle and skin that can be sacrificed -- or, more precisely, hijacked -- for that purpose.
They cut the nerves to two chest muscles, the pectoralis and serratus, at a point where those nerves have branched to go to different parts of the muscles, but far "upstream" from the point where the nerves divide into tiny fibers that attach to individual bundles of muscle fiber.
They then sew the stumps of the large nerves that once went to the arm and hand to the cut ends of the chest-muscle nerves. In the same operation, the nerves carrying sensation from the skin over the pectoral muscle are also sewn into the arm nerves.
Over several months, the arm nerves grow down the sheaths of the motor fibers and attach to the muscles. (Interestingly, the amputee assists this process by mentally "exercising" the missing hand, which helps promote a firm nerve-muscle connection.) Simultaneously, the sensory nerves grow down the sensory sheaths and into the skin.
If all goes well, a person is left with chest muscles that twitch in different places in response to such thoughts as "bend the wrist back," "move the thumb" and "clench the fingers." The person also ends up with a patch of skin about the width of a baseball that, when stroked, warmed or pricked, feels like a hand rather than part of the chest.
The bionic arm makes use of this feat of anatomical alchemy.
The prosthesis is strapped onto the shoulder stump and torso in a way that positions electrodes over the regions of the chest muscles that are responding to different "hand instructions." Those electrodes, in turn, are wired to a computer and then on to motors in the forearm and hand of the device.
When the amputee tells the fingers to close, the designated part of the pectoral or serratus muscle twitches and the electrode over it detects the signal, activating the appropriate motor.
I read things like this and I get this momentary feeling of disconnection, because in many ways, we're already living in what I think of as the distant future.
Which is totally cool, by the way.
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