Engineers at the University of Colorado Boulder have created a new film that behaves like rubber and can jump high into the air without external assistance. By simply heating it, the film can jump on its own. This development was reported in the journal Science Advances on January 18th.
The researchers believe that similar materials could be used to create "soft robots" that can jump or lift without gears or other rigid components. The material composite used in the research behaves similarly to how grasshoppers jump by accumulating and releasing energy in their legs, as stated by study co-author Timothy White.
He is a Gallogly Professor of chemical and biological engineering at CU Boulder. The research aims to create synthetic materials that mimic the natural properties seen in adaptations like a grasshopper's leg, which utilizes stored energy like elastic instability.
Hopping Discovery
The new research utilizes the unique characteristics of liquid crystal elastomers, solid and stretchy versions of the liquid crystals found in electronic devices such as laptops or televisions. The team fabricated small samples of liquid crystal elastomers, similar in size to a contact lens, and placed them on a hot plate. When heated, these films began to warp, forming a cone shape that rapidly flipped inside out, propelling the material to a height almost 200 times its thickness in just 6 milliseconds.
The lead author of the study, Tayler Hebner, who earned her doctorate in chemical and biological engineering at CU Boulder in 2022 and is now a postdoctoral researcher at the University of Oregon, said that this research presents opportunities to use polymer materials in novel ways, particularly in the field of soft robotics, where high-speed, high-force actuation mechanisms are often needed. The team discovered this jumping behavior almost by chance.
Hebner was experimenting with designing various types of liquid crystal elastomers to observe how they changed their shape under varying temperatures when Joselle McCracken, a senior research associate in White's lab, joined her to observe. They were surprised when the liquid crystal elastomer jumped off the testing stage and onto the countertop rather than the expected shape. They both were excited and confused by this unexpected behavior.
Grasshopper, Close-up of green insect on green background - stock photo
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Advanced Leaping
The team was able to determine what was causing their material to perform the high jump with the assistance of collaborators at the California Institute of Technology and careful experimentation. White explained that each of these films has three layers of an elastomer. He stated that these layers shrink when heated, with the top two layers shrinking faster than the bottom. The film contracts into a cone shape due to this incongruity and the orientation of the liquid crystal molecules within the layers. Similar to how painted vinyl siding can warp in the sun, it is similar.
The film experiences strain buildup as the cone forms before snapping abruptly. The material is knocked up as the cone inverts and hits the surface. The same film can hop multiple times without deteriorating. However, the team's liquid crystal elastomers are adaptable, unlike those poppers. The researchers can modify their films so that, for instance, they only hop when they are hot and not when they are cold. They can also give the movie legs to make it move in a certain way, as reported by Science Daily.
This kind of popping effect probably wouldn't be able to make the parts of most robots move. However, White stated that the project demonstrates what similar materials might be able to do: store an impressive amount of elastic energy and then release it all at once. According to Hebner, the project also brought some amusement to the lab. She stated that it is a compelling illustration of how the fundamental ideas we study can be transformed into designs that perform in complex and amazing ways.
RELATED ARTICLE: Grasshoppers Play Important Roles in Grasslands, Other Ecosystems; Study Also Reveals Similarities Between Their Mouth and Mammal Teeth
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