It’s straight out of a comic book: a shot of liquid silk quickly hardens into a sticky, strong fiber that can lift objects 80 times heavier. Sound familiar? Researchers have described the Spider-Man-inspired tech in a new study.
A newly-created web-like material will make many people who read comics as kids (or adults) very happy. Spider-Man is officially a step closer to existing in real life. Sure, we’re not at the swinging-from-building-to-building stage yet, but it feels like it’s not too far off.
In a new study, a team of researchers from Tufts University’s Silklab, whose goal is to reimagine natural materials as ‘living materials,’ has created the first web-slinging technology in which a fluid material shot from a needle almost immediately solidifies – and is strong enough to adhere to and pick up objects.
“As scientists and engineers, we navigate the boundary between imagination and practice,” said Fiorenzo Omenetto, professor of engineering at Tufts, director of the Silklab and the study’s co-corresponding author. “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.”
The researchers’ sticky fibers come from silk moth cocoons, which are broken down into their fibroin protein building blocks by boiling them in solution. The solution can then be shot out – extruded – through narrow bore needles to form a stream that, thanks to the right additives, solidifies when it’s exposed to air. Why moths and not spiders? Well, silk from the silk moth (Bombyx mori) has similar properties to spiders’ silk but with less structural complexity, and the raw materials are easier to come by.
As with any good comic-book-inspired discovery, the researchers found out how to replicate what spider threads achieve in nature – stiffness, elasticity, and adhesive qualities – quite by accident.
“I was working on a project making extremely strong adhesives using silk fibroin, and while I was cleaning my glassware with acetone, I noticed a web-like material forming on the bottom of the glass,” said Marco Lo Presti, research assistant professor at Tufts and the lead author on the study.
The team found that when it’s exposed to organic solvents like ethanol or acetone, silk fibroin solution forms a semi-solid hydrogel, but it takes hours. If, however, dopamine – yes, that dopamine, which makes you feel good – is added, it solidifies almost immediately. The addition of fillers – chitosan or borate buffer – created adhesive, stretchable hydrogel fibers with high tensile strength.
When tested, the extruded ‘web string’ fibers were able to lift over 80 times their own weight. The researchers successfully picked up a cocoon, a steel bolt, a laboratory tube floating on water, a scalpel half-buried in sand, and a wood block from a distance of about 12 cm (4.7 in).
The researchers foresee a range of applications for Spidey-inspired fibers, including tissue engineering, drug delivery, biomaterials, and adhesives. While they don’t achieve the strength of natural spider silk, which is about 1,000 times stronger, the researchers aim to continue to improve their sticky material.
The study was published in the journal Advanced Functional Materials.
Source: Tufts University
