New Artificial Spider Silk: Stronger Than Steel and 98 Percent Water
The silk of the humble spider has some pretty impressive properties. It’s one of the sturdiest materials found in nature, stronger than steel and tougher than Kevlar. It can be stretched several times its length before it breaks. For these reasons, replicating spider silk in the lab has been a bit of an obsession among materials scientists for decades.
Now, researchers at the University of Cambridge have created a new material that mimics spider silk’s strength, stretchiness and energy-absorbing capacity. This material offers the possibility of improving on products from bike helmets to parachutes to bulletproof jackets to airplane wings. Perhaps its most impressive property? It’s 98 percent water.
“Spiders are interesting models because they are able to produce these superb silk fibers at room temperature using water as a solvent,” says Darshil Shah, an engineer at Cambridge’s Centre for Natural Material Innovation. “This process spiders have evolved over hundreds of millions of years, but we have been unable to copy so far.”
The lab-made fibers are created from a material called a hydrogel, which is 98 percent water and 2 percent silica and cellulose, the latter two held together by cucurbiturils, molecules that serve as “handcuffs.” The silica and cellulose fibers can be pulled from the hydrogel. After 30 seconds or so, the water evaporates, leaving behind only the strong, stretchy thread.
The fibers are extremely strong – though not quite as strong as the strongest spider silks – and, significantly, they can be made at room temperature without chemical solvents. This means that if they can be produced at scale, they have an advantage over other synthetic fibers such as nylon, which require extremely high temperatures for spinning, making textile production one of the world’s dirtiest industries. The artificial spider silk is also completely biodegradable. And since it’s made from common, easily accessible materials – mainly water, silica and cellulose – it has the potential to be affordable.
Because the material can absorb so much energy, it could potentially be used as a protective fabric.
“Spiders need that absorption capacity because when a bird or a fly hits their web, it needs to be able to absorb that, otherwise it’s going to break,” Shah says. “So things like shrapnel resistant or other protective military clothing, that would be an exciting application.”
Other potential applications include sail cloth, parachute fabric, hot air balloon material, and bike or skateboard helmets. The material is biocompatible, which means it could be used inside the human body for things like stitches.
The fibers could also be modified in a number of interesting ways, Shah says. Replacing the cellulose with various polymers could turn the silk into an entirely different material. The basic method could be replicated to produce low-heat, no-chemical-solvents-needed versions of many fabrics.
“It’s a generic method to make all fibers, to make any form of [artificial] fiber green,” Shah says.
Shah and his team are far from the only scientists to work on creating artificial spider silk. Unlike silkworms, which can be farmed for their silk, spiders are cannibals who wouldn’t tolerate the close quarters necessary for farming, so turning to the lab is the only way to get significant quantities of the material. Every few years brings headlines about new inroads in the process. A German team has modified E-coli bacteria to produce spider silk molecules. Scientists at Utah State University bred genetically modified “spider goats” to produce silk proteins in their milk. The US army is testing “dragon silk” produced via modified silkworms for use in bulletproof vests. Earlier this year, researchers at the Karolinska Institute in Sweden published a paper on a new method for using bacteria to produce spider silk proteins in a potentially sustainable, scalable way. And this spring, California-based startup Bolt Threads debuted bioengineered spider silk neckties at the SXSW festival. Their product is made through a yeast fermentation process that produces silk proteins, which then go through an extrusion process to become fibers. It’s promising enough to have generated a partnership with outdoor manufacturer Patagonia.
But, as a 2015 Wired story points out, “so far, every group that’s attempted to produce enough of the stuff to bring it to the mass market, from researchers to giant corporations, has pretty much failed.”
This is the challenge Shah and his team are facing right now.
“Currently we make around a few tens of milligrams of these materials and then pull fibers from them,” he says. “But we want to try and do this at a much larger scale.”
To do so, the team is working on a robotic device to pull and spin fibers more quickly and at a larger scale than previously. They’ve had some success, Shah says, and continue to explore the process.
“We’re still in the early stages of research,” he says.
The team’s findings were recently published in the journal Proceedings of the National Academy of Sciences.