Plastic semiconductor based sensors detect muscle contraction. Light is shined into fibrous muscle, and the scattering of the light is observed. When muscle is contracted, the light scatters less, because muscle fibers are further apart. Sensors detect the changed scattering signals, and relay the information, as photocurrents, to a prosthetic limb, triggering movement. A robotic arm was controlled using this method in a recent study.
Using disposable wearable optical sensors could eliminate patient risks associated with electrical based sensors, including electromagnetic interference, pain caused by sensing needles, and immune responses.