Harvard creates a bio-inspired robot that packs a punch

When most people think of shrimp, they think of yummy seafood and very small creatures. You might not expect a small shrimp to pack a very powerful punch. However, the mantis shrimp has the strongest punch of any animal on the planet.

Acceleration is key to its incredibly strong punch, with the mantis shrimp able to accelerate its appendages faster than a bullet exits a gun. A single punch can knock the arms off a crab or crack a shell. Scientists have been researching how the mantis shrimp can generate such a powerful punch. Researchers from Harvard have leveraged high-speed cameras to learn more about the mechanics of the powerful punch. The research could pave the way for small robots that also have lots of power.

Professor Robert Wood, the paper's senior author, says the speed and force of a mantis shrimp strike results from a complicated underlying mechanism. The team constructed a robotic model of the shrimp striking appendage to study the mechanics behind the punch in detail. Researchers found that the mantis shrimp has a pair of small structures embedded in the tendons of its muscles called sclerites, acting as a latch for the appendage.

It can be thought of as the latch on a mousetrap that, when released, immediately releases all of the stored tension in the mousetrap spring. Interestingly, when the sclerites unlatch, there is a noticeable delay. Speculation suggests that while the sclerites initiate unlatching in the muscles, there is a secondary latch that controls movement while it continues to store energy.

The hypothesis hadn't been tested until this study. The team built a robot and developed a mathematical model of the movement of the shrimp. Four distinct phases of the strike were mapped, starting with the sclerites being latched and ending with the strike. They discovered once unlatched, the geometry holds the striking appendage in place until an "over-centering point" is reached and the strike begins. The robot had a striking speed clocked at 26 meters per second, which they say is equivalent to a car reaching 58 mph in four milliseconds.