The process of making a lantern. Credit: Yaoye Hong, NC State University
Researchers have taken inspiration from lanterns to create a structure that can transform into more than a dozen 3D shapes.
The polymer can be snapped into the different shapes remotely via a magnetic field, with the research team optimistic that this feature will be useful across numerous applications.
The team created the lantern-like object by taking a parallelogram-shaped polymer sheet and cutting a row of parallel lines across the middle, leaving a solid strip of material at the top and bottom of the sheet.
They then connected the right and left edges from the top and bottom together, resulting in a structure similar to a paper lantern.
“This basic shape is, by itself, bistable,” says senior author of the study, Jie Yin, a professor of mechanical and aerospace engineering at North Carolina State University in the US.
“It is stable in its lantern shape, of course. But if you compress the structure, pushing down from the top, it will slowly begin to deform until it reaches a critical point, at which point it snaps into a second stable shape that resembles a spinning top.”
As the team further experimented with the lantern’s structure, they discovered there were more ways they could manipulate it to create additional shapes.
“We found that we could create many additional shapes by applying a twist to the shape, by folding the solid strips at the top or bottom of the lantern in or out, or any combination of those things,” says first author Yaoye Hong, a post-doctoral researcher at the University of Pennsylvania, USA.
“Each of these variations is also multistable. Some can snap back and forth between 2 stable states. One has 4 stable states, depending on whether you’re compressing the structure, twisting the structure, or compressing and twisting the structure simultaneously.”
Researchers have created a polymer lantern that can snap into more than a dozen curved, 3-dimensional shapes by compressing or twisting the original structure. Credit: Yaoye Hong, NC State University
The researchers added a thin magnetic film to the strip of solid polymer at the bottom and then used a magnetic field to twist and compress the structure remotely.
“In the spinning-top shape, the structure has stored all of the energy you used to compress it. So, once you begin to pull up on the structure, you will reach a point where all of that energy is released at once, causing it to snap back into the lantern shape very quickly,” says Yin.
The team developed a mathematical model which predicts how different angles in the structure control its shape and how much energy is stored in the compressed, stable form.
“This model allows us to program the shape we want to create, how stable it is, and how powerful it can be when stored potential energy is allowed to snap into kinetic energy,” says Hong.
“And all of those things are critical for creating shapes that can perform desired applications.”
One potential application for the polymer is as a non-invasive gripper for catching fish. The team also tested out using the polymer as filter that can control the flow of water as the lantern opens and closes.
Further discussion on the applications of this lantern has been published in Nature Materials.
“Moving forward, these lantern units can be assembled into 2D and 3D architectures for broad applications in shape-morphing mechanical metamaterials and robotics,” says Yin.
“We will be exploring that.”