A wearable device mimicking muscles, tendons and ligaments of the lower leg could aid in the rehabilitation of ankle-foot disorders, U.S. researchers say. The active orthotic device using soft plastics and composite materials instead of a rigid exoskeleton has been developed by a team that includes Yong-Lae Park, an assistant professor of robotics at Carnegie Mellon University. The soft materials, combined with pneumatic artificial muscles, lightweight sensors and advanced control software allow the robotic device to achieve natural motions in the ankle, the university reported Tuesday.. The "soft" technology could be used to create rehabilitative devices for other joints of the body or even to create soft exoskeletons that increase the strength of the wearer, Park said. People with neuromuscular disorders of the foot and ankle associated with cerebral palsy, amyotrophic lateral sclerosis, multiple sclerosis or stroke could be aided by the robotic device, the researchers said. While conventional passive ankle braces can help in dealing with such conditions, their long-term use can lead to muscle atrophy because of disuse, they said. The limitation of a traditional exoskeleton device is that it "limits the natural degrees of freedom of the body," Park said, noting the ankle is naturally capable of a complicated three-dimensional motion but most rigid exoskeletons allow only a single pivot point.