ARLINGTON, Va. — How do you milk a spider?
“Very, very carefully,” according to Gareth McKinley, a professor of mechanical engineering at the Massachusetts Institute of Technology and one of the leaders of a team of MIT scientists working with the Army’s Institute for Soldier Nanotechnology.
Together, MIT and the Army are working on a program to develop a new “Soldier Suit” — a high-tech uniform that can perform a host of functions, such as adapting to different temperatures and even delivering limited medical care to sick or wounded soldiers.
The research under way at MIT is what government types call “blue skies,” meaning technologies that are at least 15 to 20 years away from becoming reality.
“These aren’t things that are rolling out next week,” McKinley said in a telephone interview from his MIT labs in Boston, Mass.
But some of the MIT approaches are further along than others, which is where the spiders come in: McKinley’s team is looking at ways to use spider silk to make the Soldier Suit’s integrated body armor much lighter and more flexible.
The fragile, delicate stuff that makes up cobwebs helping to stop bullets?
The idea isn’t nearly as far-fetched as it sounds.
“Silk is a very fine, very tough fiber,” McKinley said, something warriors throughout the ages have taken advantage of, particularly in Asia.
“Japanese and Chinese warriors used vests made of silk 1,000 years ago as protective garments,” McKinley said.
Those old vests were made not from spider silk, however, but the silk most people are familiar with, which is spun by mulberry worms, McKinley said.
Researchers have found that spider silk is even stronger than normal silk. In fact, in terms of the amount of energy the spider fibers can absorb before they break — a crucial measurement in the world of ballistics, or the science of making something “bullet proof” — “spider silk is 100 times better than steel, and 10 times better than Kevlar,” McKinley said.
So if spider silk’s properties are so well known, what’s keeping it out of today’s body armor?
Interestingly, it isn’t because there is a problem producing enough of the stuff, which is where the “how do you milk a spider” question comes in.
Not that people haven’t made the attempt, including the famous French general Napoleon Bonaparte, “who tried farming spiders during the French Revolution” in order to produce a new kind of silk, McKinley said.
Unfortunately, the critters are rather cranky and uncooperative, making them poor candidates for mass production.
“Spiders are incredibly carnivorous and territorial, neither qualities which are good farming characteristics,” McKinley said. “Napoleon failed.”
Fortunately, spider silk “isn’t anything mysterious; it’s actually just another protein,” called ‘spidroin,’ McKinley said.
That protein means the simple answer to “how do you milk a spider?” is: You don’t.
You milk goats.
Special goats, that is, who produce spider protein thanks to a cutting-edge “genetic recombinant” process developed by a commercial company in Canada called Nexia Biotechnologies Inc.
Nexia has a proprietary process to take the silk-protein producing gene out of spiders and insert it into goats, who excrete the protein in their milk.
From there, Nexia scientists simply separate the spidroin from other components in the milk, ultimately producing a powder that they market to researchers around the world.
And that’s where the snag comes in: reconstituting the powder and spinning it into a fiber that is strong enough to be useful.
Army researchers at the Massachusetts-based U.S. Soldier Systems Center, better known as Natick Labs, have tried to work with the spider silk powder, “but they had great difficulty trying to spin the material,” McKinley said. “They got fibers that looked like glass fibers: very brittle.”
Researchers have now determined that something unknown happens in the spider’s abdomen that allows the creature to extrude the flexible, strong silk fibers it needs for its webs.
So, in order to make the silk effective for body armor, “the trick is to mimic the conditions under which the spider” spins its web, McKinley said.
He and his MIT team are working with a breed called the Golden Orb-Weaving Spider to try and figure out just what those conditions might be.
The Golden Orb was chosen “because it’s fairly big, so you can get a lot of silk protein out of it,’ McKinley said — about 10 micro liters per spider, or a drop the size of a baby’s tear.
The work involves squishing a lot of spiders, McKinley said. “We haven’t figured out a way to actually milk them.”
The researchers know they have a long way to go. “We need a much better understanding of fluid dynamics,” among other challenges, McKinley said.
But “this is an engineering problem, and it can be solved.”
However, the silk isn’t going to be a “silver bullet” that will solve all the Army’s weight problems with body armor, McKinley cautioned.
“Have you ever run into a spider web? Remember how far it can stretch?” McKinley said. “At the moment, it’s way too elastic” to completely replace more conventional bulletproof materials, he said.
Instead, the Army is working toward developing a composite mix of the silk and Kevlar for its Soldier Suit, McKinley said.
“Kevlar is great, and it probably can’t be beaten,” he said.