Kirigami for friction modulation in footwear. Steel kirigami surfaces were attached to the shoe soles (middle). The undeformed (top) and deformed (bottom) configurations of the kirigami shoe grip are illustrated. The spikes are activated (shown in the magnified view, bottom right) through changes in the curvature of the shoe soles during walking to actively enhance the frictional properties between the sole of the shoe and walking surface, and reduce the risk of slips and falls.
Falls and subsequent complications are major contributors to morbidity and mortality, especially in older adults. Here, by taking inspiration from claws and scales found in nature, we show that buckling kirigami structures applied to footwear outsoles generate higher friction forces in the forefoot and transversally to the direction of movement. We identified optimal kirigami designs capable of modulating friction for a range of surfaces, including ice, by evaluating the performance of the dynamic kirigami outsoles through numerical simulations and in vitro friction testing, as well as via human-gait force-plate measurements. We anticipate that lightweight kirigami metasurfaces applied to footwear outsoles could help mitigate the risk of slips and falls in a range of environments.
Reference: Nature Biomedical Engineering
Katia Bertoldi (Applied Mechanics)
2019-2020 Harvard MRSEC (DMR-1420570)