Navy looks to 'slime' threats from sharks to missiles
Hagfish are a bit like underwater Spidermen. When they're attacked by a predator, they shoot out a slimy substance that can seal the mouth and clog the gills of said attacker, so they can make an escape. Now, A team of US Navy scientists and engineers have figured out a way to synthesize the slime with the goal of equipping the military force with a valuable new material that could do everything from repelling sharks to providing ballistics defense.This recalls a scene from Ghost Busters near the end of the movie where the fearless fighters get "slimed" by a ghostly creature. This sounds like an even more effective defensive measure to thwart attacks.
Although hagfish are mostly blind eel-like bottom feeders, the defensive slime they produce is mighty indeed, and has even been compared to spider silk. It consists of two components, thread-like proteins and mucin, a gelatinous lubricant. Inside the animal, the threads, which are only 12 nanometers in width but up to 15 centimeters in length, are tightly coiled. When the slime is shot out into seawater, the proteins holding them together dissolve and the threads spring open. This unique mechanism means that a small tube of slime could quickly expand into a large underwater defensive shield.
"The coiled up thread behaves like a spring and quickly unravels upon contact with water due to stored energy," said Materials Engineer Dr. Ryan Kincer. "The mucin binds to water and constrains the flow between the micro channels created by the thread dispersion. The interaction between the thread, mucin, and seawater creates a three-dimensional, viscoelastic network. Over time, the thread begins to collapse on itself, causing the slime to slowly dissipate. Studies have shown the hagfish secretion can expand up to 10,000 times its initial volume."
While hagfish slime has long been talked about as a new biomaterial, keeping a tank of the slimy critters on hand for manufacturing purposes just wouldn't be practical. So Kincer and biochemist Josh Kogot figured out a way to make the substance in the lab by enlisting the help of E. coli bacteria. They engineered the bugs to produce two of the proteins normally made by the hagfish, called alpha and gamma. They then combined them in solution where they assembled into the slime.
"The synthetic hagfish slime may be used for ballistics protection, firefighting, anti-fouling, diver protection, or anti-shark spray," said Kogot. "The possibilities are endless. Our goal is to produce a substance that can act as non-lethal and non-kinetic defense to protect the warfighter."