The Spectacular Synthesis of Spider Silk

How bioengineering could bring greater sustainability to the apparel industry.

A strip of blue cloth with a section that has red stripes on top of a yellow background. A small spider dangles off of the end of the cloth.

The idea that one day the clothes you wear will be made from spider silk, or maybe even mushrooms, might sound very… Californian. You know, a little over-the-top earthy and too good to be true.

But then again, back in the 1950s no one thought a mysterious oil-based fiber would be ubiquitous in clothing. But hey, polyester did pretty well.

David Breslauer ’05

For David Breslauer ’05, the co-founder and chief scientific officer at Bolt Threads, a bioengineering company in Emeryville, Calif., the potential of the spider and the mushroom represent not just another way to make apparel, but a way to bring greater sustainability to the clothing industry.

“I’m hoping to get my materials in your closet,” Breslauer acknowledges about Bolt, which gained national attention for developing a lab-grown spider silk that was first spun into a necktie and then captured the interest of designer Stella McCartney, who has used the company’s materials in her high-profile designs. Bolt Threads has since applied their technology to a variety of product lines and mushroomed into a company that has raised $200 million in funding and employs more than 100 people.

“But really,” Breslauer says, “the overall goal is to seek out problematic materials and leverage what nature has evolved over billions of years—which are usually extraordinarily complex and intricate processes—in order to solve the problems in front of us today.”

It wasn’t a simple web to weave. But UC San Diego’s wide range of courses helped shape Breslauer for what was to come.

“I had a lot of freedom to explore,” he says. “I got both a great education in the humanities and social sciences, as well as the engineering side. That’s an invaluable base of knowledge with which to build a business, particularly one at the intersection of fashion, material science, and biotech, which all carry their own challenges. There’s a lot of tension in every direction.”

At the heart of Bolt Threads, however, is innovation. The company designs biomaterials at the molecular level and scales them to commercial quantities. It’s an end-to-end process—discovering something in a lab, then problem-solving and developing means that allow for mass production. Founded in 2010, Bolt Threads is now venturing into the production realm, but that was only after Breslauer spent some time wandering in the research wilderness.

After earning a degree in bioengineering, the Revelle College alumnus began graduate work at UC Berkeley in computational biology, which involves the application of computer science to the modeling of the structures and processes of life.

“I wanted to get my hands dirty and actually build things,” he recalls. One of those things was a microfluidic device—essentially a chemistry or biology lab compressed to the size of a microchip. Breslauer had kept an eye out for what kind of chip to make, and biomimetics—replicating nature to improve engineering for new materials, devices, and systems—was hot.

“I kept my eyes on spiders,” he says. “How do they make such interesting fibers so easily? After searching through the literature, I learned that the way a spider makes silk—how it turns the silk molecule into a fiber, that is—was very similar to the microfluidic devices I was learning to make. So I thought, how can I replicate a silk gland with a microdevice?”

Breslauer built a device that operated like a silk gland, but he needed spider silk polymer to test it. Then he heard about two guys at UC San Francisco who were programming a microbe to make silk protein.

“Total serendipity,” Breslauer says. “They were trying to make silk protein, I was trying to make silk protein into fiber. It all went from there.”

But talk about trial and error: The three founders of Bolt Threads each spent five years in graduate school figuring out how to work with silk, and after that, “We really started the company rebuilding our entire technology from scratch,” Breslauer says. Because while a college lab may offer tools that allow for developing devices quickly, that path doesn’t necessarily lead to the ability to mass produce.

“The lab tools will never scale up, and the chemicals that work very well on the lab bench, turns out you can’t use them on a large scale,” because they’re too expensive or not necessarily safe, Breslauer says. “It was a lot of painstaking development.”

Which is understandable, given the ambitious endeavor to replicate arachnid evolution. Spiders have silk-producing glands in their abdomen that contain a liquid form of the chemical components to produce silk. When a spider wants to produce a length of solid silk, it uses special combs on its legs to pull out a solid strand.

Bolt Threads has no such glands and leg combs. What the company does instead is create DNA sequences that mimic spider silk proteins, which become a yeast that is brewed and can grow rapidly as it ferments. In this process, the yeasts make protein that is ultimately extracted into threads.

In other words, it’s a protein-based microfiber inspired by spider silk, as opposed to the hydrocarbon-based microfiber we all know as polyester.

In 2017, Bolt Threads spun that microfiber into a necktie as a proof of concept. The company made and sold 50 of them—not mass production, but the beginning of a breakthrough.

Fast Company named Bolt Threads one of the most innovative companies for 2018, pointing out that the fashion industry is among the world’s biggest polluters, starting with the resource-intensive cultivation of raw materials such as cotton, wool, and silk. By contrast, Bolt Threads has proven that materials like these can be manufactured in labs.

Yet where sustainability may be built into Bolt Threads materials by design, other factors like durability and consistency are not so easy to come by. Getting the spider silk to work effectively in clothing took many revisions. At one point in the process, the material shrank by roughly 40 percent. In spiders, the property is called supercontraction and is a subject of scientific study.

“Our initial biggest challenge was making the fiber strong enough to turn it into a textile,” says Breslauer. “We worked extremely hard on the processing, but were so myopically focused on strength, we forgot other things, like washability. Once we washed the textile, it completely shrank. That won’t work, of course, so we went back to the science to understand the molecular mechanisms behind the problem and designed around them.”

Whether it’s problem-solving in proteins or problem-solving for an entire industry, it’s exactly this kind of challenge that drives Breslauer every day.

“We played around with a lot of things that could be niche, but, ultimately, we looked across the industry and asked ourselves, ‘What does it take to make a fiber that’s going to solve a problem, not just something that has novelty?’” he says. “In the end, we fundamentally believe in building transformative technologies.”