Around 92 million tons of textiles are discarded every year around the world. Over 85 percent of that waste ends up in landfills, amounting to a garbage truck-full every second, even though much of it could be recycled. But recycling fabrics is a complicated problem, because they are generally blends, and it is hard to tell what a fabric is made of.
An accurate way to label and trace fabrics from when they are made until their end of life would go a long way in realizing a functional circular economy for the apparel industry. Researchers at the University of Michigan now report a novel technology for this: a special tracer fiber that encodes unique information about a fabric’s composition and origin, and can be directly woven into a fabric and read much like a barcode.
The fiber, inspired by butterfly wings, is engineered to have an optical signature that is readable using hand-held or high-throughput infrared imaging techniques commonly used in industrial facilities for sorting materials. It could help track a textile over its lifetime of store shelves and customer use. And then, when the garment is discarded, the fiber label could be read for easy sorting and recycling.
“Our unique approach is a small, easily implemented change that can make the whole system work better,” says materials science and engineering professor Max Shtein who led the work reported the work in the journal Advanced Materials Technologies.
A recent study by Fashion for Good showed that three-quarters of low-value, post-consumer textiles—almost 500,000 tons per year in Europe alone—are readily available for recycling. Knowing the precise makeup of the fabric—how much cotton, spandex and polyester is in it, say—is critical for recycling.
But this information about where a textile was made and with what materials, is usually attached to clothing via a standard care label that is easily removed or eroded, Shtein says. And it’s not always accurate. A study of over 10,000 articles of post-consumer clothing found that almost a third did not have a legible care label and, of those that did, 41 percent of labels were inaccurate.
The labeling fiber that Shtein and his colleagues made is more robust because it can be incorporated directly into the fabric. “The fiber itself is easy to make, but challenging to fake,” says Brian Iezzi, lead author of the paper.
The researchers start with a raw material that is a mix of two different plastics arranged in dozens of alternating layers. acrylic and polycarbonate. The combination of the two clear materials bends light to create optical effects that look like color; this phenomenon gives butterfly wings their shimmer.
Heating and pulling the raw material gives hair-thin fibers. By adjusting the mix of materials and the pulling speed, the researchers tuned the fiber to create the desired optical properties and ensure recyclability.
Iezzi says that they can already create kilometers of the fiber barcode in a very short time frame in the lab. The team has also demonstrated that the fibers can be integrated into fabrics using industrial equipment that textile makers use today. Since the materials for the fiber are commodity plastics that are easily available worldwide, the fiber should add a low cost of around 25 cents to garments.
“Because of the scalable manufacturing method and the low material cost for the fibers, we think that this photonic barcode could be ready for commercial integration on a large-scale in a short time frame, potentially within a few years,” he says.
Source: Brian Iezzi et al. Polymeric Photonic Crystal Fibers for Textile Tracing and Sorting. Advanced Materials Technologies, 2023.
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