The fibers designed by the Cambridge team are spun from a soupy material called hydrogel, which, depending on the chemical recipe, is comprised of up to 98 percent water. The remaining 2 percent is made up of silica and cellulose — both natural materials.
By manipulating specific chemical interactions, scientists can pull long single fibers out of the hydrogel, held together in tight molecular structures known as cucurbiturils. These individual fibers are thinner than a human hair, but can be “braided” into thicker fibers.
“A single supramolecular fiber is around six micrometers in diameter,” co-author Darshil Shah of Cambridge’s Department of Architecture, said in an email. “Human hair is around 80 micrometers in diameter, and spider silk is around five micrometers. In making a braided material, we combine multiple fiber strands — between 10 to 100, say.”
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All industrial textiles use yarns or braids of some sort, Shah said, but their recipe for synthetic spider silk has several benefits. The most immediate advantage is to their approach is the fibers self-assemble at room temperature, held together by a “supramolecular host-guest chemistry,” which allows manufacturers to avoid dealing with toxic substances or working in extreme heat.
Shah said the new process can be used to make traditional textiles, but also so-called “technical textiles” that are much tougher than your average pair of jeans. For instance, the fibers can be woven into shrapnel-resistant military clothing, sailcloth for boats, or lightweight fabrics for parachutes and hot-air balloons.
The fibers also have potential biomedical applications.
“Since the fiber is made from natural, biodegradable material — silica and cellulose — it's fully biocompatible,” Shah said. “There are numerous opportunities for exploitation in biomedical applications where energy absorption is critical — such as devices for back or spine injuries. By altering the chemistry and introducing tiny amounts of other materials, we can use these fibers for sensing applications and health monitoring.”
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Shah said that the new chemical process could potentially be used to improve other kinds of synthetic fibers too.
“Industrially produced synthetic fibers rely on toxic solvents and high energy methods, with temperatures well exceeding 200 Celsius — even up to 1,500 Celsius in the case of carbon fiber,” Shah said. “Whereas we are able to produce fibers using water as a solvent, and at ambient temperatures and pressures.”
The new Cambridge process was very much informed by nature, Shah said. After all, spiders don't need toxic chemicals or fiery temperatures.
“Spider silk is our inspiration, as spiders have evolved over hundreds of millions of years to produce superb fibers using low energy.”
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