New Product Technology


Soft, Robotic Device May Have Implications in Assisting Patients with Ankle-Foot Disorders

OrthoticDesignResearchers at Carnegie Mellon University recently spotlighted the development of a soft, wearable device engineered to mimic the muscles, tendons, and ligaments of the lower leg. The device, says assistant professor Yong-Lae Park, PhD, could hold promise in assisting in the rehabilitation of patients with ankle-foot disorders, such as drop foot.

A news release from the university reports that Park worked with collaborators at Harvard University, the University of Southern California, MIT and BioSensics, to develop the active orthotic device. To build the device, researchers say, they used soft plastics and composite materials, rather than a rigid exoskeleton. The inclusion of soft materials blended with pneumatic artificial muscles (PAMs), lightweight sensors positioned on the top and side of the ankle, and advanced control software is intended to allow the robotic device to achieve natural motions in the ankle.

The sensors are reportedly comprised of a touch-sensitive artificial skin, featuring thin rubber sheets that contain long microchannels filled with a liquid metal alloy. Once the rubber sheets are stretched or pressed, the release notes, the shapes of the microchannels change. This causes a change in the electrical resistance of the alloy.

The release states that the robotic device would be suitable to assist individuals with neuromuscular disorders of the foot and ankle linked to cerebral palsy (CP), amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS), or stroke. Researchers explain that the soft orthotic device is designed to mimic the biological structure of the lower leg. Its artificial tendons attached to four PAMs, which correspond with three muscles in the foreleg and one in the back that control ankle motion.

The prototype was also capable of generating an ankle range of sagittal motion of 27 degrees. Yet, Park adds, the soft device is more challenging to control than a rigid exoskeleton; and required more sophisticated sensing to track the position of the ankle and foot, and a more intelligent scheme to control foot motion.

Park also notes that additional work is required to improve the wearability of the device, including the introduction of less bulky artificial muscles than the PAMs used in the project. The project’s findings appear in the journal Bioinspiration & Biomimetics.

The device has yet to be tested on patients.

Watch it in action here

Source: Carnegie Mellon University