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Portraits In Posthumanity: Claudia Mitchell

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In 2004, Claudia Mitchell lost her left arm in a motorcycle accident. Two years later, she became the first woman to have a bionic arm - a prosthetic limb that she controls with her mind.

The robotic arm comes from the Rehabilitation Institute of Chicago, and was developed for $3 million. Mitchell, who used to peel bananas using both feet and one hand, can now carry items, lift cups, and move her prosthetic arm almost as naturally as her real one.


How does it work? Mitchell's arm is "myoelectric," which means it picks up electrical signals coming straight from her brain, down her nerves. Electrodes help the signals jump from her body, to the prosthesis, which uses a computer to figure out which motion Mitchell is thinking about.

Surgeons made this process easier by routing many of the nerves from Mitchell's arm to her chest. While there are some weird results of this process - for example, when she showers, Mitchell can feel the water hitting a phantom "arm" when it hits her chest. There are several spots all over her chest muscles that, when touched, trigger feelings like "that's my elbow" or "that's my hand." When she identifies those, researchers attach electrodes to those spots and program the computer in her arm to recognize signals from them as "elbow" or "hand" signals. This gives her fairly granular control over the arm.


The arm's designer, Todd Kulken, recenty co-wrote an article where he explains the way his myoelectric limbs work:

There are two ways in which prosthetic arms are currently controlled. One way is to use other body motions, such as shrugging the shoulders, to pull on a series of cables and operate the hand, wrist, or elbow. These prostheses are called "body-powered" prostheses. The other way is to read the tiny electrical signals generated by muscles when they contract, and use these signals from remaining muscles to control a motorized arm.

These muscle signals are read by small electrical antennas called electrodes. For example, someone who has lost their arm above the elbow may use their biceps and triceps muscles to control their prosthetic hand. The prosthesis could be programmed to interpret signals from the biceps muscle as "open the hand" and signals from the triceps muscle as "close the hand." These prostheses are called "myoelectric prostheses."

Here you can see some of the motions Mitchell is capable of with her bionic arm.

As one of the first volunteers to undergo the nerve-rerouting surgery, as well as to get a brain-controlled prosthetic, Mitchell is a true posthuman pioneer. She has a robot arm that is controlled with her mind. It doesn't get more cyborgian than that.


Photos via Washington Post (top image) and Getty/Win McNamee.