Slowly but surely, we are making good on the gadgets we imagined, as kids, that the future would hold. Penny Brown’s video watch from Inspector Gadget? Check. The Starfleet tricoder from Star Trek? Almost there. But web-shooting? Web-slinging? That wasn’t one we really thought would make the crossover. And it wasn’t exactly in the plans for the scientist who has made the strong, sticky air-spun web a reality either, Marco Lo Presti, from Tufts University’s Silklab.
Back in 2020, Lo Presti, a research assistant professor in biomedical engineering, was working on the challenge of underwater adhesives. The first material he chose to work on was made up of silk and dopamine, a popular combination because it mimics the way that mussels stick firmly to rock surfaces in water—something that has been useful in other applications.
“While using acetone to clean the glassware of this silk and dopamine substance,” he says, “I noticed it was undergoing a transition into a solid format, into a web-looking material, into something that looked like a fiber. I showed the vials to Fio, and we immediately started thinking about how we could make a remote adhesive [a substance that sticks to an object from a distance] out of it.”
Fio is Fiorenzo Omenetto, professor of engineering at Tufts and “puppeteer” of the Silklab. “We’d like to say that every experiment is painstakingly planned with equations and lots of forethought but it’s really about connection,” he says. “You explore and you play and you sort of connect the dots. Part of the play that is very underestimated is where you say “hey, wait a second, is this like a Spider-Man thing?” And you brush it off at first, but a material that mimics superpowers is always a very, very good thing.”
Before Lo Presti could turn his attention to these accidental webs, though, he had to complete his paper on underwater adhesives using biomolecules, which he did in 2021. A lot of the Silklab’s work is “bio-inspired” by spiders and silkworms, mussels and barnacles, velvet worm slime, even tropical orchids—so working out if this sticky web could become something useful might seem like an easy side-step for the team.
However, Lo Presti points out that while the new material does mimic spider threads, “there is no spider able to eject, to shoot a stream of solution, which turns into a fiber and does the remote capturing of a distant object”. This was something new, for the real world at least.
But as the research paper in Advanced Functional Materials notes—enter fictional characters. In Stan Lee and Steve Ditko’s original 1960s comic books, starting with Amazing Fantasy #15, Peter Parker builds a “little device”, one fastened to each wrist and triggered by finger pressure, to produce strands of ejectable ‘spider webs’. By the time of the mid-2000s Sam Raimi Spider-Man films, the web-shooting switched from a wrist-worn spinneret gadget to an organic part of his superhero transformation.
Video: Marco Lo Presti, Tufts University Silklab
From Science Fiction Into Reality
At the real-life lab in Medford, Massachusetts, the true web-slinging evolution began when Lo Presti and his colleagues shot a thin stream of their silk fibroin (Japanese silk moth cocoons, boiled down and broken into proteins) and dopamine combination through a needle. This was originally ejected straight into a ‘bath’ of acetone, which triggers the substance’s solidification into a hydrogel.
The team then decided to add this all-important acetone into the outer layer of a coaxial needle, surrounding the silk and dopamine in the inner needle layer to enable the liquid to shoot straight into the air. As the acetone evaporates mid-air, the dopamine speeds up the substance’s solidifying process, creating sticky, strong spun fibers by pulling water away from the silk—something that would usually take hours.
With the obvious pop culture inspiration in mind, this was a place the team worked hard to get to. “We were looking at doing something in air,” Lo Presti says, “so adapting and creating the engineering device, the study of the flow, the coaxial needle, to have the fiber ejected in the air—that was where we started to get truly excited.”
The team started to experiment its strength, shooting fibers to capture and lift objects including a cocoon, a 2g stainless-steel bolt and a 5g wood block from 12cm away. Bit by bit, they fine tuned their solution with additional materials to change what it was capable of: a biopolymer named chitosan to give the fibers up to 200 times more tensile strength and a borate buffer to increase the adhesiveness to objects by 18 times.
“We can now catch an object up to 30 or 35 centimeters away, and lift an object of around 15 to 20 grams,” says Lo Presti. The silk fibers performed the best on cardboard and wood, both instantly and after ten minutes, but also work on materials like plastic, glass and metal. Testing real world conditions, the researchers used the air-spun fibers to remotely pick up a small plastic lab tube floating on water, and a stainless-steel scalpel, partially buried in sand.
So, Spider-Man capabilities when? “Everybody wants to know if we’re going to be able to swing from buildings,” says Omenetto, with a wry smile. But we’re not there yet—so far the Silklab team itself has speculated about some potential uses for the material: the retrieval of an object that’s lost underwater, perhaps, or a drone that captures something in a remote environment.
“In principle, if you have the starting material and if you can control the parameters, the baseline material properties are such that you could do amazing things,” Omenetto explains. “I mean you could probably lift a very heavy object, but that’s one of the big questions—what can you lift? Can you remotely drag something? Silk is very, very strong, it’s very tough, it can lift incredible weights but this is silk in its natural form whether it’s from the spider or the silkworm. There is not a fundamental limit in these directions.”
Lo Presti is interested to hear from anyone who has read his paper and thinks they might be in need of a web-shooting silk fiber. A few months after he published his work on the underwater adhesive, a non-profit emailed to ask if it could be used to tag sharks. “My first answer was absolutely not,” he says, “because the adhesive is too rigid, and because sharks move. But I then tried to make something and we’re still collaborating with them and working on this.”
It’s not unlikely, Lo Presti suggests, that the same could happen with this project, and that the speed, distance and strength of the object-capturing fibers could also be improved with more dedicated work from the team. These first “small” examples are to demonstrate the possibilities of the material, but improving and tailoring it for specific applications may be the key to uncovering its true potential.