Can Crustaceans Really Stop a Speeding Bullet?
Lobsters are the caped crusaders of the sea. Their body armor is tough. Their claws are strong. Their meat is tasty. But maybe there is more to these bottom-dwelling crustaceans than meets the eye. Scientists at MIT and Harvard think so.
A recent study from Ming Guo’s laboratory at MIT, with collaborators from Harvard University, has cracked the wondrous properties of a lobster’s underbelly. Published in the journal Acta Biomaterialia, the researchers determined both the ‘mechanics and mesoscopic structure’ of American Lobster membranes, with an eye towards developing flexible, yet durable, body armors.
Guo, in a discussion with MIT News, stated that he developed the idea for a lobster-inspired body armor while eating a lobster and noticing ‘that the transparent membrane on the animal’s belly was difficult to chew’. While researchers have long studied the rock-hard exoskeleton of crustaceans, their softer, watery insides have remained a mystery.
In the study, the MIT team studied the white, cartilaginous-like material on the underside of lobster tails and found that it possessed astounding material properties. Though it consists of about 90% water, it is as hard as rubber and is ‘fault tolerant’, meaning that a cut into one layer will not negatively impact the performance of other layers. These properties, coupled with its elastic nature, make it ideally suited for flexible armors.
The authors then performed a serious of tests to determine the properties of the bio-derived material. They found that it could withstand forces up to 23.36 MPa (more than 23 million Pascals), which is roughly equivalent to the water spray pressure of high-powered pressure washers or the chamber pressure of a high-powered air gun.
Though consisting of mostly water, the ‘active ingredient’ in this material is chitin, a chemical polymer consisting of many sugars linked together. Similar to cellulose, chitin is among the most abundant chemicals found in nature — it makes up the hard shells of beetles, spiders and ants.
Chitin is impressive because it can easily be stacked into a three-dimensional lattice, which adds strength without severely impacting flexibility. In the research article, the authors mention that the lobster underside consists of ‘tens of thousands of layers’ that are stacked in a manner akin to the wood fibers in plywood.