Go go robo-ankle! A robotic device kitted out with artificial muscles could help people with cerebral palsy strengthen their foot and ankle muscles, helping to improve their walking.
Yong-Lae Park of Carnegie Mellon University and his colleagues took a standard knee strap, ankle brace and shoe, and attached four pneumatic artificial muscles. These are flexible tubes that contract when filled with air, mimicking the action of biological muscles. Three artificial muscles link the knee with the front of the ankle while a fourth is placed on the back, in an effort to replicate the normal configuration of muscles and tendons.
The artificial muscles are powered by a small canister of compressed air and controlled by circuitry strapped above the knee, which moves the user's foot through a range of predefined motions designed to strengthen weak muscles while they are seated. Future versions might be wearable while their user goes about their day-to-day life. "Controlling the device using the wearer's motion or muscle intention is our ongoing and future work," says Park.
At the moment, patients wear ankle braces that provide support but don't allow for a range of movement. The idea behind the project was originally to help people with long-term conditions, but Park says it might also be useful for some injuries. "The device could be used for short-term ankle rehabilitation as well, for example muscle training and exercise after cast or splint removal."
"It's a really good idea," says Margaret Phillips of the University of Nottingham, although she thinks it might only help with neuromuscular disorders, because patients recovering from broken ankles can rely on their own muscles. Its high-tech appearance might also be an issue, she adds. "You'd have quite a substantial proportion of patients who wouldn't want to wear it just because it looks odd."
Journal reference: Bioinspiration & Biomimetics, DOI: 10.1088/1748-3182/9/1/016007
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