This $20 Wearable Fabric "Arm" Harvests Energy As You Walk, Lifts Up to 10lbs Safely

Engineers at Rice University and Harvard University have come up with a pneumatic wearable "arm" designed to offer an extra limb to those who need it — and deriving its power entirely from the wearer's walk.

"Census statistics say there are about 25 million adults in the United States who find it difficult to lift 10 pounds with their arms," explains co-lead author Anoop Rajappan of the problem the team set out to solve. "That’s something we commonly do in our daily lives, picking up household objects or even a baby."

The solution: an "arm" that's made from fabric, designed to hug the body when not in use — but when required to inflate and extend outwards to grab and grip objects, weighing up to 10 pounds, and moving them with a curling motion without any need to rely on the wearer's own muscles.

The limb is powered by an energy-harvesting device located in the wearer's shoe: As the wearer walks, the pressure on the insert fills an energy storage bladder worn around the waist with air with a conversion efficiency of around 20 per cent. As well as driving the extra limb, the same system has been demonstrated providing assistance with lifting the wearer's own limb — using a bellows-like actuator located under the armpit.

"The stiffness of the [energy harvesting insert] foam is about on par with a typical shoe insert," says assistant professor of mechanical engineering Daniel Preston of the prototype. "We wanted to make sure this felt like something you'd actually want to have inside of your shoe."

The device is also remarkably affordable, costing just $20 in materials, and robust enough to survive repeated machine washing. "The fabrication approach uses techniques that are already employed in the garment industry," Preston explains, "things like cutting textile sheets and bonding them with heat and pressure. We're ready to think about translating our work towards products.

"Now that we're providing the power, we can tap into all the existing work on actuation. This would include things like gloves that help people close their hands, assistance at both the elbow and shoulder joints and other devices that still rely on typically rigid and bulky power supplies that are either uncomfortable or require being tethered to external infrastructure."

The team's work has been published under open-access terms in the journal Science Advances.