An electrical generator built into a backpack can make walking more efficient by taking the strain off leg muscles, while also harvesting a small amount of electrical power. The device reduces the energy required to walk by more than 3 per cent and could also charge small electrical devices.
Many exoskeletons have been designed to make humans stronger or more efficient. Some have a power source and actively assist limb movement. But Michael Shepertycky at Queen’s University in Kingston, Canada, and his colleagues have now created an entirely passive system that reduces the effort required to walk.
The design resists the forward swing of the leg during a stride and slows it before the foot strikes the ground, something that usually requires movement of the Achilles tendon.
The device weighs 1.3 kilograms and fits into a small backpack, while two thin cable runs from there down to ankles and strap around the legs. As the foot swings forward during a stride, this cable resists slightly by spinning an electrical generator.
Currently, that generator doesn’t even power the small amount of electronics in the backpack. But Shepertycky is confident that, with small improvements, it will not only do that but also be able to charge other small devices, such as a smartphone.
He and his colleagues tested the device on a treadmill with 10 male walkers and found that it reduced the metabolic effort of walking by 3.3 per cent, while also converting the removed energy into roughly 0.25 watts.
“Within a couple of minutes of walking with the device, it does feel pretty natural. If you were to walk with the device or go for a hike with it, at the end of the day, you’d feel less tired,” he says. “This could really help hikers that are walking all day, or even mail carriers or nurses at the end of their shift to be a lot less tired.”
Current tests have focused on walking on flat ground, but Shepertycky hopes that future experiments will show efficiency gains in walking up and down hills and at different speeds. It is possible that such a system could even make running more efficient. “We may be able to assist running and beat some records for the marathon,” he says. “It’s hard to say.”
The team has patented the device and is exploring commercialisation. Shepertycky believes that because it is passive and doesn’t require motors, movable joints or a solid frame, it should be “a fraction” of the cost of active exoskeletons.
Journal reference: Science, DOI: 10.1126/science.aba9947
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