Researchers have demonstrated how kirigami can be used as a ‘tool’ for scientists and engineers to create strong, rigid objects out of soft materials. It could be applied to make inexpensive, lightweight, and deployable structures, such as temporary emergency shelter tents that are strong and durable but can also be easily assembled and disassembled.
A close-up view of the weight-bearing kirigami structures created by Xinyu Wang while working in Randall Kamien's lab. Each raised triangle platform is supported by neighboring flaps (shown outlined in blue) that work together to hold the structure in place without tape or adhesive. Credit: Erica Brockmeier
The Japanese art of origami (from ori, folding, and kami, paper) transforms flat sheets of paper into complex sculptures. Variations include kirigami (from kiri, to cut), a version of origami that allows materials to be cut and reconnected using tape or glue.
But while both art forms are a source of ideas for science, architecture, and design, each has fundamental limitations. The flat folds required by origami result in an unlockable overall structure, while kirigami creations can't be unfolded back into their original, flattened states because of the adhesive.
Taking inspiration from both art forms, researchers describe a new set of motifs for creating lightweight, strong, and foldable structures using soft materials. These kirigami structures can support 14,000 times their weight and they can easily be flattened and refolded because they don't require adhesives or fasteners. Published in Physical Review X, the work was conducted by visiting graduate student Xinyu Wang and Professor Randall Kamien of the University of Pennsylvania in collaboration with Simon Guest from the University of Cambridge.
While the newly designed single triangle wasn't particularly strong on its own, the researchers noticed that when several were arranged in a repetitive design, the force they could support was much greater than expected. "Here was this structure that didn't require tape, it had cuts, and it was really strong," Kamien says. "Suddenly, we have this system that we hadn't anticipated at all."
With the help of Guest, the researchers realised that two deviations from the group's typical kirigami rules were key to the structure's strength. When the walls of the triangles are angled, any force applied to the top can be translated into horizontal compression within the centre of the design. "With the vertical ones, there's no way to turn a downward force into a sideways force without bending the paper," says Kamien. They also found that the paper-to-paper overlap from leaving the cut flaps in place allowed the triangles to press up against their neighbours, which helped distribute the vertical load.
Thanks to Wang's ‘inspired’ design and Kamien's burgeoning collaboration with Wang and her advisors Jianguo Cai and Jian Feng , the possibilities for future ideas and designs are endless. "There were things about this study that are totally outside the scope of what a physicist would know," says Kamien. "It was this perfect blend of what I could do and what she could do."
Read the full study here
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