Researchers at Georgia Tech and Emory University have developed a device that makes walking up and down stairs easier. It’s a set of energy-recycling stairs that store a person’s energy during descent and return energy to the next person who climbs the stairs.
The spring-loaded stairs compress when someone comes down the stairs, saving and storing 26% of the energy otherwise dissipated through impact and braking forces at the ankle. When going up, the stairs give people a boost by releasing that stored energy, making it 37% easier on the knees than using conventional stairs. The low-power device can be placed on existing staircases and doesn’t have to be permanently installed.
Each stair is tethered by springs and equipped with pressure sensors. When a person walks downstairs, each step slowly sinks until it locks into place and is level with the next step, storing energy generated by the user. It stays that way until someone walks upstairs. When a person going up the stairs steps on the sensor on the next tread up, it releases the latch on the lower step. The stored energy in the spring is also released, lifting up the stair and the back leg.
The researchers say their initial idea was to use energy-recycling prosthetic shoes to help people going up stairs.
“Unlike normal walking where each heel-strike dissipates energy that can be potentially restored, climbing stairs is actually very energy efficient; most energy you put in goes into potential energy to lift you up,” says Karen Liu, an associate professor in Georgia Tech’s School of Interactive Computing. “But then I realized going downstairs is quite wasteful. You dissipate energy to stop yourself from falling, and I thought it would be great if we could store the energy wasted when coming down descent and return it to the user when climbing them.”
“Walking down stairs is like tapping the breaks of your car while revving the engine,” says Lena Ting, a professor 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.”
Prior to designing the device, the researchers didn’t expect that the stairs would actually ease the impact of going downstairs. The spring in the stairs acts as a cushion and brake, rather than the ankle. The gentle downward movement reduces work done by the trailing ankle, which is what keeps you balanced and prevents you from falling too fast on normal stairs.
Liu initially got the idea for the project when she attended a conference and saw an ankle brace that stored and released energy. Her 72-year-old mother has no problems walking but has difficulty climbing steps, and Liu knew she wouldn’t wear special sneakers just for stairs. So she decided to make smart stairs that act like the shoe.
“Current solutions for people who need help aren’t very affordable. Elevators and stair-lifts are often impractical to install at home,” Liu says. “Low-cost, easily installed assistive stairs could be a way to allow people to retain their ability to use stairs and not move out of their homes.”
The researchers think the temporary stairs could also be helpful for those recovering from surgery or pregnant women—people who only need help for short periods of time and don’t need to permanently alter their homes.
