Harnessing Origami-Inspired Metamaterials with Magnets

Jie Yin, a researcher at NC State University, is a pioneer in the emerging field of kirigami engineering. Kirigami is the Japanese artform of cutting paper in precise, dynamic designs.

“You may have heard about origami, which is folding,” says Yin, a professor in the Department of Mechanical and Aerospace Engineering at NC State and a 2024 recipient of the Presidential Early Career Award for Scientists and Engineers. “Kirigami is cutting, so it creates new opportunities for the materials, for the structures, and they have totally new behaviors.”

Researchers are exploring how cutting engineered materials with kirigami’s repeating geometric patterns creates metamaterials with unique mechanical properties. For instance, in 2024, Yin’s lab developed a cube capable of transforming into over 1,000 shapes — potentially paving the way for versatile, load-bearing robots used in space exploration.

More recently, Yin’s research team explored how kirigami-cut elastic materials can snap open and closed into new shapes — and how magnets can help control the sequence in which the materials unfold. The new work advances our understanding of metamaterial behavior such as its ability to absorb kinetic energy.

“If you cut a T-pattern into a polymer sheet you’ve created a metamaterial, because you’ve changed the properties of the material,” says Haoze Sun, first author of a paper on the work and a Ph.D. student at NC State. “If you pull the metamaterial sheet, all the cuts essentially pop open at once. These openings create a mesh-like pattern and extend the length of the sheet.

“We were curious about what would happen if we incorporated magnetic materials into the polymer and magnetized the sheet. Would this ‘snapping’ behavior change? And what we found was surprising.”

Yin’s research team discovered that the rows in the mesh pattern snapped open one by one rather than all at once. This happened because magnets held the sheet together, while gravity pulled them apart.

They also found that the rows of each sheet opened in a different order — and that each sheet repeated that same order each time they were stretched. Small, unavoidable defects controlled the sequence of how the material snapped open. Since the flaws didn’t disappear, the order remained the same. “That, in itself, was interesting,” Sun says.

The researchers then experimented with clamping multiple magnetized sheets next to each other. With two sheets placed back-to-back, their magnetic fields pushed away from each other. This caused the rows to open in order from top to bottom 90% of the time — revealing two interesting findings. 

“First, magnetizing the material makes it open in a sequence instead of all at once,” Yin says. “Second, we can make that sequence more predictable by lining up the materials correctly.”

The team also experimented with dropping a ball onto a net-like metamaterial and found that magnetism allowed the material to absorb energy. When the material was unmagnetized, the ball bounced; adding magnetism made the material absorb 30% more energy. 

“We can control how much energy it takes in by changing the strength of the magnets,” Sun says. ”Stronger magnets absorb more energy.”

The team’s research on using magnets to control metamaterials holds potential in a range of applications, including guiding sound or light waves, building flexible robots, and improving medical tools.

“We’re excited about future directions for this work,” Yin says.

This article is based on a news release from NC State University.