It responds to the user's muscles that remain in their residual limb. Muscles generate small electrical signals when they contract, these can be detected by sensors placed on the surface of the skin. The bionic arm uses these, so that contracting different muscles produces specific movement, such as opening or closing a fist.
In the video Michael McLoughlin, from Johns Hopkins University's Applied Physics Laboratory, explains how the Modular Prosthetic Limb (MPL) works, while Air Force Tech Sgt Joe Delauriers practises using it.
One of the next steps is to work on using brain implants to control the arm, when residual muscle contraction is lost. Initial work with the MPL has used electrodes to tap into brain cell signals, allowing the patient to stroke his partner's hand with his robotic one.
Bron + afbeelding: BBC News