Humans domesticated the silworm around 7,000 to 5,000 years ago in China. The special properties of strength and flexibility of silk were recognized early.
Spider silk is even stronger. Its properties are eyebrow-raising, according to Fiorenzo Omenetto, director of the Silklab at Tufts University. Five times stronger than steel by weight but completely organic, it’s “the stuff of superheroes,” says Omenetto.
Indigenous groups, such as Australian Aborigines, have long used the silk of giant tropical spiders (like the Golden Orb Weaver) to create fishing lines and nets. In the 1880s, a French missionary in Madagascar, Jacob Paul Camboué, built a machine to harvest silk from Golden Orb Weavers. He proved the silk was strong enough to be woven on modified looms, producing fabric that was a sensation at the 1900 Paris Exposition.
But that's as far as it went. No one could find a commercial use of this versatile, strong, flexible substance, or even figure out how to mass-produce it.
Then, in the 1980s and 1990s, researchers such as Fritz Vollrath and Randy Lewis conducted detailed studies quantifying the tensile strength of "dragline silk" (the spider's safety line). They confirmed it could have a tensile strength of roughly 1.1 to 1.5 GPa, which is comparable to high-grade steel. (GPa stands for "Gigapascal." It is a unit of stress used to measure how much pull or "tension" a material can withstand before it deforms or breaks.)
Enter the geneticists and the wild idea to mix spider DNA with the silkworm's DNA. Spiders are ravenously cannibalistic and cannot exist in large groups, as silkworms do, because they would soon eat each other. Why not do the next best thing and give silkworms the ability to spin out spider silk by altering a few genes?
Those spider silk–spinning silkworms, all genetically modified, live at the Lansing, Michigan, research center of biotech firm Kraig Biocraft Laboratories. Kraig is just one of several companies around the world that have made breakthroughs in manufacturing spider silk. Or a very close analog. Those silkworms can’t quite match spider silk’s superhero-level physical properties just yet, but there is enough spider gene in the mix to give their silk fibers special qualities. Other companies have charted a different path—one less reliant on worms munching mulberry leaf cake—but with the same goal. “The goal is to mimic, and eventually surpass, the performance of natural spider silk, and then push it toward real-world applications,” says Wenbo Hu, a spider silk expert at Southwest University in central China. “We’re getting incredibly close.”
For the first time, the long-hyped supermaterial dubbed “supersilk” seems to be real. But the start-ups and genetic engineers who’ve spent years (and millions of dollars) pursuing this holy grail are now having to reckon with a question they’d been able to ignore in the quest for supersilk at scale: Once you make a supermaterial, what do you do with it? The answers, it turns out, aren’t as obvious as they’d imagined.
Indeed, a new, lightweight bulletproof vest has been one of the original goals of the domestication of the spider silk-spinning silkworm. That effort initially failed because the vests proved to be impossible to scale up and manufacture in bulk.
In the 2010s, technology came to the rescue with the development of CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats). At the molecular level, CRISPR uses proteins to "unzip and cut" DNA. This allows a scientist to insert a DNA strand with the desired attributes from one lifeform into another.
In this case, it's the spider silk the insect manufactures that is piggybacked onto the silkworm's silk manufacturing process, which then produces a much-improved silk. As NGO points out, the genetically altered silkworm "can’t quite match spider silk’s superhero-level physical properties just yet," but they're getting close.
The hybrid silk "had six times the toughness—the measure of a material’s capacity to deform without breaking—of Kevlar," reports NGO.
“This material is not gonna stop a 747,” says Kraig Biocraft Laboratories founder and CEO Kim Thompason, “but it’s better than regular silk. It’s stronger and more flexible.” It’s not quite spider silk, but it is supersilk. And most important, it’s scalable.
Most companies looking to develop spider silk into commercial products have been at it for decades. Every time they've felt they were close to a real breakthrough, the bottom fell out, and their efforts went for naught.
Is this time different? Are we now on the cusp of a materials revolution that will impact us in ways too many to imagine? The first place to look for change will be in the medical and healthcare fields.
In the case of spider silk, the quest to unlock the secrets of its strength and flexibility has led to a new understanding of protein structures and how those translate into performance at the microscopic scale. “Beyond fabric, recombinant spider silk proteins can be processed into diverse forms—films, hydrogels, sponges, microcapsules, and nanoparticles,” says Xingmei Qi, who researches spider silk–based therapeutics at Soochow University. “What once seemed nearly impossible is now becoming technically and economically feasible.”
The applications being explored would be revolutionary: Spider silk–influenced gels and biofilms can coat catheters and surgery meshes, reducing infections and blood clots. They can line wound dressings and improve cosmetics. At the nanoscale level, they become Legos, giving gene jockeys the ability to design new molecules one amino acid at a time, forming shapes and functions that go beyond anything available in nature’s pharmacy.
Imagine chemotherapy so targeted that only the cancer is attacked while healthy cells are left alone? Or a vaccine that could carry "delicate immune system–stimulating molecules to their targets and release them at slow, sustained rates," as NGO explains. Supersilk nanocapsules carrying the vaccines or chemo drugs programmed to target a specific organ would radically increase the effectiveness of chemo drugs and vaccines while making them safe.
Is that future right around the corner? The companies say it is. I'll wait to pop the cork on the champagne until it becomes a reality.
