Researchers at North Carolina State University have shown that magnetizing elastic metamaterials can control the sequence in which they unfold, according to a March 20 announcement. The study, published in Science Advances, highlights a new way to program the mechanical response of materials by using magnetic forces.
This research is significant because it advances understanding of how metamaterials—materials engineered with specific patterns—can be manipulated for practical uses such as energy absorption and robotics. By controlling the order in which sections of a material snap open, scientists can design materials with tailored properties for various applications.
Haoze Sun, first author and Ph.D. student at North Carolina State University, said, “If you cut a T-pattern into a polymer sheet you’ve created a metamaterial, because you’ve changed the properties of the material. 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.” Sun added that incorporating magnetic materials led to surprising results: instead of snapping open all at once, rows opened one at a time due to competing magnetic and gravitational forces.
Jie Yin, corresponding author and professor of mechanical and aerospace engineering at NC State, explained further: “We found that instead of snapping open all at once, the rows in the pattern snapped open one at a time, because the magnetic force is trying to hold the pieces of the sheet together while the force of gravity is trying to pull them apart.” The researchers also discovered that each sheet consistently repeated its unique snapping sequence due to small defects present in each sample.
The team experimented with placing multiple magnetized sheets together so their magnetic fields repelled each other. This arrangement caused rows to snap open sequentially from top to bottom most of the time. Yin said, “First, we can make the metamaterial snap open sequentially, rather than all at once, by magnetizing the sheet. Second, we can drastically reduce randomness in that behavior by aligning these metamaterials properly.”
The findings also showed practical benefits for energy absorption: “We found that the magnetized elastic metamaterial could absorb 30% more kinetic energy than the unmagnetized metamaterial,” Sun said. By adjusting internal magnetic strength, researchers could control how much energy was absorbed.
Yin concluded by noting potential future applications: “The ordered snapping sequence can find potential applications in guiding wave propagation, reconfigurable robotics, and biomedical devices.”
The research was supported by grants from organizations including the National Science Foundation and European Union projects.
