A spider’s silk has long been admired by scientists for being incredibly robust – five times stronger than steel – as well as flexible, elastic, soft and stable at high temperatures. They are properties that could be put to use in a wide range of consumer products.
But attempts to produce the silk in large amounts have proved tricky, not least because spiders are cannibalistic and territorial so collecting the material is not economically viable. The thread itself is so fine that it would take millions of spiders to produce a kilogram of silk.
Materials scientists have been trying to a crack the problem and, in northern California, a solution appears to have been found by Bolt Threads, which will unveil next year the first products which use fibres developed to replicate the unique benefits of spider silk. The goal is to make clothes which are softer, stronger, lighter and more durable.
After six years working in labs behind closed doors, the scientists who lead Bolt Threads have recently unveiled the details of their system allowing them to effectively replicate spider’s silk on a large scale, producing fine fibres made up of sugar, water, salts and yeast.
In Emeryville, a city close to San Francisco, the researchers studied the proteins which make up the spider silk. They then developed their own proteins “inspired” by the natural silk.
The process starts with genes being put into yeast, in a similar way to making beer. The yeast produces silk protein in a liquid form during the fermentation. This liquid silk can then be turned into a fibre through a process called wet-spinning, where it is squeezed through small holes into a bath, creating the solid substance.
Dan Widmaier, chief executive and co-founder, says it was a major breakthrough.
“You have the ability of a very sophisticated modern technology to reimagine an industry which has been around for a very long time, one of the cornerstone industries in the world which has not seen a lot of innovation and disruption since the 1930s when petroleum polymers came around with nylons and [when] polyesters in the 1950s came along.
“That is a really exciting concept because you are seeing this steady march of science, engineering and technology finding newer and better things to help improve our society as we get more people on the planet, [with] limited resources and trying to always push the envelope of what we are trying to do in a sustainable way.”
The fibres will come to market in two ways. Companies will use them in their own products as an added ingredient. Bolt Threads – which now has more than 50 staff in its Californian headquarters and has raised $40m worth of financing – is also launching its own brand to unveil the product, although the exact details remain a secret.
“All the things that make the earliest sense are the things that nature gives us the template for. Stronger, softer, lighter, stretchier, anti-microbial,” Widmaier says. The cost of the new fibres will be high. “It will definitely be a premium product at launch.”
It is not the first time that a spider’s web has proved an influence for manmade products. Orthox, an Oxford-based company has developed small implants for the knee, using silk proteins to make a strong, curved rubber-like material. Widmaier says Bolt Threads technology could be used as part of medical devices inside the body, in the future.
Just as all spiders’ silk is not the same – the arthropods spin different types of silk depending on what it will be used for – the Bolt Threads silk can also be adaptable.
“When we talk about spider silk, most of us are thinking the one that is the basis for the Spiderman franchise – stretchy and stronger than steel and tougher than Kevlar. That is really only one silk. Each spider you find … have seven different kinds of silk they are making with different mechanical properties with different protein sequences for different niches that they need to fill. The idea there is that nature has already given us a template for different performance properties which match or exceed what we can do with petroleum or hydrocarbon chemistry today,” Widmaier says.
The glories of silk
Stronger than steel, flexible, more elastic than other fibres and stable at high temperatures – just a few of the benefits of spider silk which have fascinated scientists. Suggested uses for the silk are as a bulletproof vest, due to its strength, although because the material is so extendable, it would catch a bullet but not before it went through the body. The uses of silk are diverse – up until the first world war, it was even being used in the crosshairs of optical instruments.
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