It sounds like something out of a comic book: a material that shoots from a needle and solidifies into a fiber capable of lifting objects 80 times its own weight. But we’re not talking fiction here.
Researchers at Tufts University’s Silklab have developed a silk-based sticky fluid that instantly turns into a fibrous material when ejected, evoking the gravity-defying, web-slinging powers of the iconic Spider-Man.
However, as much as you may want to channel your inner superhero, it’s not yet strong enough to carry a person across the city skyline. Still, for the first time, we have a real web-slinging technology.
“As scientists and engineers, we navigate the boundary between imagination and practice. That’s where all the magic happens,” Fiorenzo G. Omenetto, one of the study authors and director of Silklab, said.
“We can be inspired by nature. We can be inspired by comics and science fiction. In this case, we wanted to reverse engineer our silk material to behave the way nature originally designed it, and comic book writers imagined it,” he added.
Making of the Spider-Man silk fiber
The creation of the silk fiber came about by accident. Marco Lo Presti, who is the lead study author and an assistant professor at Tufts University was trying to create powerful adhesives using silk fibroin, the protein produced by silkworms (Bombyx mori) that gives silk its strength and flexibility. This is when he noticed something unusual.
“While I was cleaning my glassware (containing silk fibroin) with acetone, I noticed a web-like material forming on the bottom of the glass,” Marco Lo Presti, said.
He discovered that when mixed with acetone, silk fibroin turns into a semi-solid hydrogel. Add some dopamine to this mix, and the liquid solution almost instantly solidifies into sticky silk fibers when exposed to air. This improved the fiber’s adhesiveness and tensile strength significantly.
However, Presti and his team didn’t stop there. They wanted to further enhance the properties of this material, so they added chitosan. It increased the adhesiveness and tensile strength of the spider-man-inspired silk fiber by 18 and 200 times, respectively. Chitosan is a naturally occurring substance found in the shells of insects and crustaceans. It is non-toxic, biodegradable, and used as a preservative in various medicine and food items.
Next, they created a small device with a needle that shot the silk liquid toward any object a user wanted to grab. During the testing, they successfully lifted steel bolts using the silk fiber. The bolts were 12 cm (5 inches) away from the needle and weighed about 80 times more than the silk fiber.
“We are demonstrating a way to shoot a fiber from a device, then adhere to and pick up an object from a distance. Rather than presenting this work as a bio-inspired material, it’s really a superhero-inspired material,” Presti said.
Why not use spider silk?
While this new material draws comparisons to Spider-Man’s web-slinging, the researchers worked with silk from silkworms — like the kind you find in clothing — rather than spider silk.
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Spider silk is one of the strongest natural substances, even exceeding steel in strength relative to its weight. And compared to silk fibroin from silkworms, spider silk is nearly a thousand times stronger, durable, and flexible.
However, what makes the silk fiber special is that it solidifies very fast, and since it is made in a lab, scientists have complete control over its properties. They can modify the adhesiveness and strength of the material based on the requirements — making it an attractive option for numerous applications including soft robots, industrial adhesives, drug delivery, biodegradable sensors, tissue engineering, etc.
In contrast, natural spider silk does not have a single formula for its production, as its properties can vary widely among different spider species. Previous efforts to make artificial spider silk have been disappointing and several promising spider silk-based startups have folded over the years.
The researchers now plan to further enhance the properties of their silk fiber. While swinging between skyscrapers may still be a distant fantasy, the possibilities in material science are looking stronger than ever.
The study is published in the journal Advanced Functional Materials.