Mar 8 2019
What is common between sea slugs, pizza slices¸ and a potential design for upcoming soft-bodied robots? They all possess frilly surfaces, and a deeper understanding of the amazing geometry of frilly surfaces may enable an imminent generation of extremely flexible and energy-efficient soft-body robots to move.
The intricate folds of a frilly surface like kale leaves or coral reefs are surfaces, which are generally referred to as “inflected non-smooth surface” by mathematicians. This surface alters the direction in which it bends.
People have looked at these hyperbolic surfaces for 200 years, but nobody has thought about the role of smoothness in relation to how these things move, their mechanics. Nobody saw a relevance to these things until now.
Shankar Venkataramani, Mathematician, University of Arizona.
At the 2019 American Physical Society March Meeting in Boston, Venkataramani will present his team’s study on sea slugs, non-smooth surfaces, and potential robotic applications.
According to Venkataramani, until now, physicists usually assumed that natural frills take place when the balanced forces existing between concurrent stretching and bending of a sheet make the surface to crease or crumple.
Conversely, in a new study performed along with doctoral students Toby Shearman and John Gemmer and Hebrew University physicist Eran Sharon, Venkataramani demonstrated that there can be non-smooth surfaces that are frilly yet unstretched at the same time.
“The idea that these frilly surfaces don't have stretching in them, that was completely counterintuitive,” he stated.
Venkataramani further observed that the study also demonstrated that changes from one form to another seem to need extremely less energy. This finding is significant because the potential to change the surfaces’ geometry has major implications for their strength and hence their capability to act on the environments. When one picks up a soggy pizza slice, it tends to create a mess but “put a little curvature and it becomes stiff and you can eat it,” Venkataramani said.
After developing the mathematics to elucidate these surfaces, Venkataramani’s team modeled non-smooth thin films that had six up-and-down parts and then speculated how they would actually move.
We realized that nature already solved the problem millions of years ago. Some sea slugs and marine worms use this geometry to get around.
Shankar Venkataramani, Mathematician, University of Arizona.
Now, the challenge is to accurately establish how the unique swimming gait of the soft-bodied and highly flexible marine invertebrates, like the Spanish dancer sea slug, is associated with their non-smooth geometry, he said.
The answer might give “a potential avenue for building soft robots that are energy-efficient and extremely flexible,” concluded Venkataramani.
The 2019 APS March Meeting presentation “On the unusual swimming gaits of sea-slugs,” by Shankar Venkataramani and Kenneth Yamamoto, will take place on March 7th, 2019, at 3:30 p.m. in room 255 of the Boston Convention and Exhibition Center.