How it works2

The world's first bionic woman, Claudia Mitchell, can now open her drawer with her prosthetic arm by thinking "arm- grab and pull". In essence, she can make complex movements with her prosthetic arm by just thinking about it, like any normal limb. This is possible for two reasons. First, once a limb is amputated the brain is still capable of sending signals to the amputated limb and secondly, many nerves are still capable of receiving information. In the case of Claudia, her shoulder was dissected to assess the nerve endings that would communicate information to the hand. These nerve endings were rerouted to a working muscle group, i.e. her chest. These nerve ending are connected to electrodes on the chest. Each of these electrodes fire one of six motors that move the prosthetic. Furthermore, since they are individual electrodes, the person can think and make these individual movements simultaneously. This results in a more realistic movement.

At MIT, Dr. Hugh Herr is creating a sieve integrated circuit electrode. This can be compared to a neighbor stealing cable television. If the wire is cut and spliced, an additional signal can be picked up. In this case, a nerve is cut and allowed to "regrow" itself into the electrical circuit. Now, when a signal is sent through the nerve, the electrical circuit picks up the signal and routes it to the prosthetic actuator. Not only will the prosthetic pick up the signal, it will also be able to send signals to the central nervous system. "With [the sieve electrode], you have bidirectional controllability, where you can actually close the loop. Imagine a future with this type of technology, that an amputee would not only be able to walk across a sandy beach, but could actually feel the sand against his prosthetic foot." Dr. Hugh Herr (6)