Kirigami-Inspired Shoe Bottom Coatings to Slip-Proof Your Shoes
Most of us have been there before. Walking on a slippery surface, your legs give way, you fall over and you're left sprawled on the floor looking like Bambi on ice while your friends fall over themselves laughing.
Thankfully, a group of engineers at MIT have put their heads together to find a solution to our woes.
Inspired by the Japanese paper cutting art of kirigami, a variation of origami, MIT engineers designed a friction-boosting material that can be used to coat the underside of shoes in order to give them a strong grip on slippery surfaces, including ice.
Japanese art inspiring scientific research
Unlike origami, the Japanese art of kirigami involves cutting as well as folding. The team of researchers drew on this to create an impressive shoe coating that opens up when a wearer is placing their foot on a surface, creating a spiky surface.
After a series of laboratory tests, the researchers determined that when people wearing these kirigami-coated shoes walked on an icy surface, they could walk more steadily as their shoes generated more friction than uncoated versions.
The researchers say that, aside from preventing the occasional embarrassing face plant maneuver amongst friends, these shoes might also have an important application in helping the elderly, as they are more prone to falling and causing serious injury.
“Through this work, we set out to address the challenge of preventing falls, particularly on icy, slippery surfaces, and developed a kirigami-based system that facilitates an increase of friction with a surface,” Giovanni Traverso, an MIT assistant professor of mechanical engineering told MIT News.
Traverso, along with Katia Bertoldi, a professor of applied mechanics at Harvard University, is one of the senior authors of the study, which is published today in Nature Biomedical Engineering. MIT Research Scientist Sahab Babaee is the lead author of the paper.
Kirigami has a history with science
This isn't the first time the arts of kirigami and origami have been used as a muse by scientists: origami-inspired untethered soft robotics machines were recently unveiled by scientists at Caltech; MIT scientists also recently unveiled kirigami-inspired bandages that stick securely to the skin as well as sensors that can help soft robots orient themselves in space; Harvard researchers created a snake and kirigami-inspired robot.
In the case of MIT's kirigami shoes, the paper cutting technique helped the researchers to create a coating that remains flat while a person is standing still, but opens up into small spikes during natural foot movement. The intricate pattern used can be applied to a thin sheet of metal or plastic.
“The novelty of this type of surface is that we have a shape transition from a 2D flat surface to a 3D geometry with needles that come out,” Babaee says. “You can use those elements to control friction, because the sharp needles can pop in and out based on the stretch that you apply.”
The researchers tested the friction generated by a variety of patterns on different surfaces, including ice, wood, vinyl flooring, and artificial turf. They found that all of the designs boosted friction, though the best result came from a pattern of concave curves.
Using a force plate, an instrument that measures the forces exerted on the ground, the team then tested volunteers using the shoes and found that the amount of friction generated was 20 to 35 percent higher than the friction generated by normal shoes.
Preventing injuries and falls
As MIT News reports, the scientists are now considering whether to design shoes that already have the coating incorporated, or whether to create a thin sheet that can be applied when needed.
The researchers say the coating could help the elderly as well as people who work on slippery surfaces, such as wet or oily environments.
“We’re looking at potential routes to commercialize the system, as well as further development of the system through different use cases,” Traverso says.
Falling on your face and being the butt of your friends' jokes might become a thing of the past. More importantly, this clever technology could help prevent accidents for the elderly as well as people working in hazardous environments.
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