Engineers from Georgia Tech and Emory University have designed a staircase that takes the load off when climbing up to bed. The energy-recycling steps store up the energy of people heading downstairs and use it to give them a boost on the way back up.

Loaded with springs and equipped with pressure sensors, steps sink to meet those below when they detect footsteps. The step then locks into place, storing the energy generated by the user’s bodyweight compressing the springs inside.

Each step stays locked in the compressed position until they detect footsteps travelling in the opposite direction. When a person steps on the sensor on the next tread up, a latch is released and the lower step returns to its original position, gently lifting the user’s back leg.

‘Braking’ your fall

Walking up a flight of stairs is remarkably energy efficient. Most of the chemical energy we put into climbing up is transferred into potential energy. Going down, however, a lot more energy is spent to stop us from toppling over.

“Walking down stairs is like tapping the brakes of your car while revving the engine,” explained Lena Ting, professor of biomedical engineering in the Wallace H. Coulter Department of Biomedical Engineering at Emory and Georgia Tech. “Your legs use a lot of energy bracing each step to avoid falling too fast. Our stairs store that energy rather than wasting it.”

Designed to limit the energy spent in climbing upwards, the researchers didn’t initially expect the steps to ease the impact of going down as well.

Yun Seong Song, the post-doctoral researcher at Georgia Tech who built the device, explained how this works. “The spring in the stairs, instead of the ankle, acts as a cushion and brake,” he said. “The gentle downward movement alleviates work by the trailing ankle, which is what keeps you balanced and prevents you from falling too fast on normal stairs.”

Following in their footsteps

Karen Liu, one of the study’s authors and associate professor at Georgia Tech’s School of Interactive Computing, was impressed by the concept of energy-recycling shoes she had seen at a conference. Designed to give users a spring in their step when climbing the stairs, she quickly realised a more practical use for the technology.

“Current solutions for people who need help aren’t very affordable,” she said. “Elevators and stair-lifts are often impractical to install in the home.”

The researchers think their low-cost, easy-to-install, temporary stairs could allow people to retain independence and stay in their own homes following loss of mobility through injury or aging. The temporary installation could also prove beneficial for those needing short-term help getting upstairs, for example, pregnant women or people recovering from surgery.

Image credit: Yun Seong Song et al 2017. Demonstrating ascent on the energy recycling stairs.

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