Why is a seahorse’s tail square? Scientists have been examining why the square structure of the tail makes for better armour and gripping abilities than a tail with a cylinder structure.
The lead scientist involved in the study is Michael Porter, who is an assistant professor in mechanical engineering from Clemson University. Porter said, “Almost all animal tails have circular or oval cross-sections—but not the seahorse. We wondered why,”
They established that the square shaped tails are better at delivering impact resistance, absorbing energy and gripping. It was also established that the square plates in the tails structure makes it stiffer, stronger and more resistant to stress all at the same time. Interestingly, when any single one of these characteristics is strengthened it normally weakens one or more of the others.
The team established that the square plates moved with only a single degree of freedom when crushed: they slide. In contrast to this measurement a circular plate will shift by two degrees as they rotate and slide. This means the square plate structure can absorb greater levels of energy prior to failure.
3D printing was used to reconstruct a sea horse tail, which allowed the team to mimic biological designs. These artificial tails were then tested through being twisted, bent and crushed to establish behaviour. The 3D printing process was also used to produce a more regular cylindrical tail that went through the same tests.
Gripping and grasping
The team established a seahorse’s tail bends in a way that means it can grasp objects in the creature’s line of sight. The testing proved that the square tails are optimised for forward grasping. The square tails were more limited in their movement than the round ones. When the round versions were twisted they took much more energy to return them to their original position.
The team discovered that the joints within the square tails existed in the exact point that failure was experienced in the cylindrical tails. The square tails also outperformed the cylindrical versions in all crushing tests.
The potential uses for these findings include improving the structure of robotic arms that are required to grip. As well as scaling up the structure for robotic use, it could be reversed to a smaller size to produce medical tools like catheters.