Mantis shrimp can strike hard during a fight: in one swing, they chop off a crab’s hand or pierce a snail’s shell. Scientists decided to use these skills to create robots.
Scientists have long been interested in the mechanisms that underlie the movements of the praying mantis shrimp. Researchers have previously been able to visualize and measure these movements, but the mechanism itself remains a mystery.
In the new work, the researchers modeled the strike mechanics of a praying mantis shrimp and created a robot that mimics these movements.
The speed and strength of the blows of the praying mantis shrimp is a consequence of a complex underlying mechanism. If we build a robot in the form of an appendage of a mantis shrimp, then we can study these mechanisms in as much detail as possible.
Many small organisms, such as frogs, chameleons, and even some plant species, can move ultra-fast: they accumulate elastic energy and quickly release it using a click mechanism that looks like a mousetrap.
Mantis shrimp move in a similar way: they have two small structures embedded in the tendons, called sclerites, and act like a latch. As soon as the crustacean removes the latch, the spring immediately releases the stored energy. However, praying mantis shrimp do not have specific muscles that are unlike other crustaceans, so it is not clear what, if not muscles, controls these movements.
The authors of the new work built a robotic model of a mantis shrimp, after which they developed a mathematical model of its movement. The researchers mapped the four phases of the strike, starting with the snapped sclerites and ending with the actual appendage strike. They found that indeed, after the latch is removed, the appendage stays in place until it reaches the centering point, and then the latch is released.
The researchers simulated this process on a shrimp-sized 1.5-gram robot. It did not reach the speed of a praying mantis shrimp, but it made strikes faster than other similar devices.