Changing Threads

Cécile Chazot creates recyclable, sustainable textiles with new functions and traits. By Carolyn Wilke

Image: All photographs by Matthew Gilson

When Cécile Chazot was a young girl, her mother taught her how to sew. By age 5, Chazot could hem a pair of pants. And since then, working with textiles has been a thread running through her life, including her research at Northwestern.

Chazot grew up in Brive-la-Gaillarde, a town in rural France, among family who sewed. Her mother made entire garments for Chazot, including ornate silk pieces, and her great-aunt worked as a seamstress, making custom garments for private clients. Around age 18, Chazot asked her mom to teach her to sew clothes from patterns. That opened her world to constructing all types of clothing, from everyday shirts and pants to three unique dresses for her wedding in 2021.

Chazot, who sews, knits and crochets, turns to her creative outlets to recharge. “Doing those crafty things is my oxygen,” she says. (In fact, she’s currently making a suit for herself in Northwestern purple.) But Chazot’s fascination with fabrics has also fueled her research on the future of textiles and what’s needed to manufacture them.

Her decades of working with cloth taught her how fabrics — whether drapey, stretchy or stiff — can be transformed into garments. “I know how the fabric needs to behave,” she says. This knowledge helps her design textiles that strategically connect the fibers’ properties to their best possible applications — for instance, using breathable fibers in clothing.

Today Chazot is the Julia Weertman Professor in Materials Science and Engineering in the McCormick School of Engineering, where she directs the Sustainable Polymer Innovation (SPIn) Lab. The group focuses on creating sustainable textiles with new chemical properties. “We’re trying to think about the solutions we needed yesterday,” she says — solutions needed to address the environmental toll of textiles.

Not much has changed in the textile industry since the mid-20th century, when chemists discovered the nature of polymers — long molecules made up of repeating smaller units — and began using them to create synthetic fibers with fantastic properties, Chazot says. With these polymer-based fibers, DuPont and other companies created performance materials — such as super stretchy spandex and strong and lightweight nylon — whose properties surpassed those of natural fibers or imitated them at low cost.

While naturally occurring polymers, including rubber, cellulose and wool, exist, many of the polymers used in textiles don’t occur in nature. And synthetic textiles have a heavy carbon footprint. For each ton of synthetic polymer-based textiles produced, 17 tons of carbon dioxide equivalents are generated. Apparel now accounts for some 20% of industrial water pollution worldwide, mostly due to fabric dyeing. And after their use, 85% of textiles discarded in the U.S. end up in landfills or are burned.

Chazot and her team are striving to boost the functionality of existing polymers and design new, more sustainable materials — ones that not only are functional and high-performing but also can be manufactured with a far lower carbon footprint and recycled more easily.

Cécile Chazot stands smiling, facing the camera, with a blue lab coat over her burgundy sweater and black jeans.

Cécile Chazot, assistant professor of materials science and engineering, in her lab

With Chazot’s forays into polymer chemistry, polymer physics and manufacturing, one might think that her background was tailor-made for researching textiles. For a long time, though, Chazot wasn’t interested in academia.

Her experience at a technical and scientific high school fueled her interest in aerospace composites — material mashups that often use textiles in the form of carbon or woven-glass fibers. After high school, Chazot went to a rigorous preparatory school in Paris and then was accepted to Mines ParisTech, a prominent engineering research institution, for her master’s degree in materials science and engineering.

As a respite from coursework, Chazot decided to spend a semester abroad doing research at the Massachusetts Institute of Technology (MIT), where she worked with physicist Mathias Kolle on structural colors — colors produced not by dyes but by the interaction of light with the molecular or physical structure of objects.

That experience changed her mind about academic research. She took a gap year to finish the project and eventually created thin films, inspired by the color-mixing texture on some butterflies’ wings, that can help make translucent microorganisms easier to image with standard microscopy equipment.

She took another semester to do research abroad at the University of Cambridge in England, working with Silvia Vignolini to study the polymer cellulose, the main component in most plants’ cell walls, and its ability to take on colors based on how its macromolecules (very large molecules) are aligned.

Remote Research

Program aims to increase involvement in materials science

During the COVID-19 pandemic, Cécile Chazot and Max L’Etoile, both MIT grad students at the time, teamed up with MIT materials scientist Jessica Sandland to create the Materials Initiative for Comprehensive Research Opportunity (MICRO) program. MICRO provides long-running remote research experiences for undergraduate students who don’t have access to such opportunities at their own college or university.

It’s an important step toward making the field of materials science more accessible, says Chazot, noting that many materials science projects include simulations, data analysis or modeling components that students can work on from afar. Remote work enables research during the school year as well, allowing students to develop greater expertise and stronger relationships with a mentor than they could during a brief stint of summer research. The program provides a crash course on materials science, professional development workshops and an in-person annual summit for all participants to connect with each other and their mentors.

MICRO’s first two years paired students with MIT faculty. Chazot expanded the program to include Northwestern researchers when she joined the materials science and engineering faculty in 2023. Chazot also mentored program participants, helping them with grad school applications and checking in on their research Experiences.

So far, MICRO has around 20 alums. Many have gone on to graduate school at high-ranking schools, including Northwestern. “These are enormously motivated and qualified students,” Sandland says. “It is exciting to watch what they’re doing after participating in this program.”

Chazot eventually returned to MIT for graduate school. She worked on a NASA-funded project to create composites using carbon nanotubes — ultrathin cylinders of carbon — with the goal of making strong, lightweight materials that would enable more efficient spacecraft. She and her grad school colleagues developed a new, scalable process to synthesize polymers within networks of carbon nanotubes and other materials used in the industry.

“The breadth and the depth of her work was very impressive,” says MIT professor John Hart, who was Chazot’s doctoral adviser. She quickly understood the problem, developed mathematical models to test her ideas and then prototyped the best approaches in the lab, performed rigorous characterization of the materials, built several new collaborations and communicated her results. “She spanned the whole spectrum,” he says. Chazot, Hart and their colleagues hold a patent on the process, and researchers in his group continue to build on her work.

The NASA project included multiple institutions beyond MIT. While most grad students only know their little piece of the puzzle, Chazot knew what the other MIT researchers were up to and how the pieces related to each other, says Greg Odegard, a materials scientist at Michigan Technological University who led the project. She was the glue holding all that together, he says. And “she’s tenacious. When she has a goal, there’s very little that’s going to stop her.”

Hart agrees: “Cécile has a compelling combination of fundamental knowledge, drive, creativity, people skills and mentoring talent to elevate others around her and lead them to do the impossible.”

Chazot designs and sews much of her own clothing and often works on pieces at Sew Design Studio in Evanston.

In 2023 Chazot joined the Northwestern faculty, eager to engineer the next generation of performance textiles by bridging her deep understanding of materials with potential applications. “Northwestern is awesome for this because the students are really excited about doing mission-driven fundamental research,” Chazot says.

Her SPIn Lab is turning to biological polymers and fibers for inspiration. “If you look at nature, it does a lot of stuff that we can’t do. Can we harness that?” Chazot says. For instance, many natural materials contain building blocks that assemble themselves into structures. Such natural materials inspire the SPIn Lab’s quest to make dye-free colors, easy-to-recycle fabrics and materials that could be used as environmental sensors, among other applications.

In a corner of Chazot’s lab, an instrument labeled “Churro” squeezes out a naturally derived cellulose-based gel material, similar to how a churro’s sweet batter is pressed through a tube-like mold before it goes into the fryer. (Each piece of equipment in the SPIn lab has a dessert’s name — owing to the group’s reputation for making excellent baked goods for the department coffee hour. A machine that heats and presses samples is called Pound Cake. And a device that heats polymers to determine the temperature at which they burn has the moniker Crème Brûlée.)

Cellulose polymer molecules, which can self-organize into a liquid crystal phase, can arrange themselves into helical structures that vary based on how the material is processed. Depending on these arrangements, the cellulose liquid crystals interact differently with light — causing them to appear as different colors. With the Churro machine, Chazot and her team use extrusion-based methods to put force on the liquid containing the cellulose polymer chains, which in turn produces films — thin, flexible layers of polymeric material — that can be any color. The researchers plan to extrude thin fibers of these gels and then weave these fibers into textiles, with the goal of creating structurally colored fibers without having to add dyes, Chazot says.

Other materials interact with light that human eyes can’t perceive, such as infrared light from derived from shrimp shells, crab shells and fungi, to make materials that reflect infrared light. By reflecting this light, which humans perceive as heat, the materials keep what they cover cool, “despite the fact that they are in bright sunlight,” Chazot says.

With modifications to the chemistry of these materials, Chazot also envisions color-changing textiles that could serve a purpose beyond fashion — as sensors for environmental pollution. For instance, fibers that change color if they bind to certain metals in water could be used to monitor the water quality of streams and rivers near dye houses that use metal-based dyes. Such color-changing materials could enable biomedical applications as well. Resistance bands for physical therapy could change color when stretched to provide a visual indicator of a patient’s effort. Or a bed mat that changes color at pressure points could prompt medical staff to reposition a patient to prevent bedsores.

Chazot pictured with blue and green colored film squares.

Cécile Chazot’s Sustainable Polymer Innovation Lab is working to make dye-free colors, easy-to-recycle fabrics and materials that could be used as environmental sensors.

Chitosan could also help give spandex fibers, which are found in most clothes, a second life. Spandex is typically unrecyclable. “So if your garment has spandex,” Chazot says, “it goes in the landfill.” This is because, in most cases, stretchy fibers contain a spandex core with another material (such as cotton or polyester) twisted around it. The spandex is so sticky that it’s difficult to strip it off the other fibers to separate them out for recycling.

But Chazot’s team has coated commercial spandex with chitosan, creating a layer that would prevent the spandex core from sticking to the surrounding fiber. Under the microscope, they’ve observed that the chitosan adheres well to a spandex core. But when exposed to a fairly mild acid, the chitosan dissolves, which would allow the cotton or polyester to come free of the spandex and be separated for recycling.

Both chitosan and cellulose are abundant, commercially available materials. Chazot hopes that the spin her group has put on these and other biomaterials can create new technologies that will someday reach the market, through startups or commercialization by textile companies.

“It’s only going to happen because we do the fundamental science,” Chazot says.

Carolyn Wilke ’18 PhD is a Chicago-based freelance science writer and editor. She studied environmental engineering at Northwestern. As an adjunct professor in the Medill School of Journalism, Media, Integrated Marketing Communications, she teaches students how to communicate their research and report on science for the public.