Grasshoppers, meet your new rival.
Engineers at CU Boulder have created a new, rubber-like film that can leap high into the air like a grasshopper—all by itself and without needing external support.
The researchers believe that similar materials could one day aid in developing “soft robots” (those that do not require gears or other hard components to move) capable of leaping or lifting.
According to study co-author Timothy White, the material system responds similarly to how grasshoppers jump by storing and releasing energy in their legs.
“In nature, a lot of adaptations like a grasshopper’s leg utilize stored energy, such as an elastic instability,” said White, Gallogly Professor of chemical and biological engineering at CU Boulder.
“We’re trying to create synthetic materials that emulate those natural properties.”
The new study uses the unusual behavior of a class of materials known as liquid crystal elastomers. These solid and stretchy polymer versions of liquid crystals are found in laptops and television displays.
In the experiment, the researchers created small wafers of liquid crystal elastomers about the size of a contact lens and placed them on a hot plate. As the films heated up, they began to warp, forming a cone that rose up until it abruptly and explosively flipped inside out, spurring the material to a height nearly 200 times its own thickness in just six milliseconds.
“This presents opportunities for using polymer materials in new ways for applications like soft robotics where we often need access to these high-speed, high-force actuation mechanisms,” said study lead author Tayler Hebner, a Ph.D. in chemical and biological engineering at CU Boulder.
Hebner and her coworkers, almost by accident, discovered this hopping behavior. To investigate how the shape of various liquid crystal elastomers changed in response to temperature changes, she experimented with designing them.
“We were just watching the liquid crystal elastomer sit on the hot plate, wondering why it wasn’t making the shape we expected. Then, it suddenly jumped off the testing stage onto the countertop,” Hebner said. “We both just looked at each other, kind of confused but also excited.”
The team carefully experimented to determine what caused their material to perform the high jump, with assistance from collaborators at the California Institute of Technology.
According to White, each of these films comprises three elastomer layers. He believes that most robots would be unable to use this type of snapping effect to move their parts because these layers shrink when heated. However, according to White, the project demonstrates what materials of a similar kind may be capable of, such as storing a significant amount of elastic energy and then releasing it all at once.
Hebner said the project also added a little fun to the lab. “It’s a powerful example of how the fundamental concepts we study can transform into designs that perform in complex and amazing ways,” she said.
The study was published in the journal Science Advances.