Seahorses are majestic but bizarre creatures. Their tails are peculiar for the animal kingdom as they are unlike those of many other tailed creatures like monkeys, mice and tigers, which all have cylindrical tails. Instead, seahorses have tails with a much more angular shape, as they are surrounded with square, bony plates.

Fascinated by this unusually square appendage, scientists decided to find out if it could be used to inspire a new generation of robotics. The seahorse, despite being a fish, doesn't use its tail for swimming. Instead, it uses it for gripping onto things like seaweed. Since these animals seem to be so adept at hanging onto this slippery foliage, scientists thought that their unique tails could be an ideal feature to try to replicate in a robot. 

Michael Porter, from the University of California, San Diego, and his colleagues therefore decided to create some computer models to find out how the seahorse's tail could be superior to cylindrical tails.

The tail modelled with square plates had some pronounced advantages over the model with circular plates. When the circular arm tried to grip something, its plates would slide and rotate, making gripping a chore. The square arm, on the other hand, did not rotate. The square plates only slid over each other, which had significant structural advantages to the circular design.

The researchers then 3D-printed their designs to test how they fared after being bent, squashed and twisted. The square model outperformed the circular one when crushed: the square shape absorbed the shock of impact where the circular plates deformed. The square design's inbuilt damage protection is something that has been difficult to achieve in silicon-based robots, so this tweak in structure could help us to develop strong, silicon robots.

^{Researchers found that the tail's square segments create more contact points with the surface that it is gripping when compared with a tail with round segments. Michael Porter/Clemson University.}

The seahorse-inspired tail did, however, have some deficiencies compared to the round tail. For example, the shape of the square plates limited the tail's movement to about half of that of the circular plates, making it less versatile. However, when twisted, the square model restored its form much faster.

The seahorse-inspired tail has potential applications of all sizes: scale it up to make a robotic arm or scale it down to create a catheter. Marc Meyers, coauthor of the study published in Science, mused that there are many possibilities.

"Human engineers tend to build things that are stiff so they can be controlled easily," said Ross Hatton, another coauthor from Oregon State University. "But nature makes things just strong enough not to break, and then flexible enough to do a wide range of tasks. That's why we can learn a lot from animals that will inspire the next generations of robotics."

[Via Science Mag]