Viscoelastic metashells jump on a preset timer

Precisely when these ‘metashells’ jump, and how high they jump, is said to be engineered into the physical structure of the materials.

“There are structures that ‘jump’ immediately when loading is removed – such as when a coiled spring is released,” said Jie Yin, corresponding author of a paper on the work and an associate professor of mechanical engineering at North Carolina State University. “We wanted to create a structure that does not rely on external stimuli and allows us to dictate the timing of the jump in advance. We have developed a technique that allows us to precisely schedule when the structure leaps into action, whether that is in seconds or hours.”

For this work, the researchers created spherical structures made of strands of polyethylene terephthalate (PET) which are connected into a complex lattice pattern. The design of the structure maximises the material’s ability to store energy. When a load is applied to the structure, it is deformed out of shape, but when that load is removed it returns to its original shape. However, PET has viscoelastic material properties so does not snap back into its original shape immediately.