The fibers can range from just a few micrometers in thickness to a few millimeters, and they can be hundreds of meters long. You can also weave other elements in the fiber, too, such as nanowires (as researchers to measure the tension), electrodes or optical fibers. And the robotic limb would not need external, bulky heat sources to activate the fibers. And if you bundle the fibers, they could provide automated, precise control.
While this is still a lab experiment, there's a lot of potential. Tiny medical robots could work on your body from inside, while larger bots could be brawny, speedy or both. This could be especially vital for prosthetic limbs, where hydraulics and other machinery can bog them down. An artificial limb could not be more natural, but offer more comparable response time