Clever Invention Could Revolutionize Recycling of Clothes

The clothing industry is a mess. Fast fashion and the rapid-fire cycling of trends means we’re tossing out clothes at an astonishing rate. And unfortunately, we’re doing a terrible job of recycling the discards. In the United States, less than 15% of the 92 million tons of clothing and other textiles are recycled annually, meaning that over 17 million tons of textiles are sent to landfills each year.

Much of the problem lies in the fact that recyclers have a hard time knowing what exactly the item is made of, and thus, these mountains of textiles are incredibly difficult to sort. Tags are often cut off or washed until illegible, while tagless (printed) information can wear off. Missing or inaccurate knowledge about an item’s fiber composition can make textile recycling cost-prohibitive.

If only there were a way to create a tag describing the textile, which was woven into the fabric and remained invisible until it needed to be read…

Well, bingo. That’s exactly what a University of Michigan-led team has developed: Woven-in labels made with inexpensive photonic fibers, which ensure that the materials used in a garment can be easily identified.

"It's like a barcode that's woven directly into the fabric of a garment," said Max Shtein, University of Michigan (U-M) professor of materials science and engineering and corresponding author of the study detailing the new technology. "We can customize the photonic properties of the fibers to make them visible to the naked eye, readable only under near-infrared light or any combination."

As described in the study's abstract, the intrinsically recyclable, low-cost labeling system is comprised of drawn photonic fibers woven into fabrics, "characterized by near-infrared spectroscopy and short-wave infrared imaging."

A similar concept is already in use by recyclers for some materials, explains U-M’s Gabe Cherry in a press release announcing the research. “Recyclers already use near-infrared sorting systems that identify different materials according to their naturally occurring optical signatures,” writes Cherry. “The PET plastic in a water bottle, for example, looks different under near-infrared light than the HDPE plastic in a milk jug.”

Like different plastics, different fabrics also have unique optical signatures. But as Brian Iezzi, lead author of the study, explains, those signatures don’t help recyclers much because so many fabrics are comprised of a blend of materials. 

"For a truly circular recycling system to work, it's important to know the precise composition of a fabric—a cotton recycler doesn't want to pay for a garment that's made of 70% polyester," Iezzi said. "Natural optical signatures can't provide that level of precision, but our photonic fibers can."

Shtein adds that not only could the labels make recycling more feasible, but could be used to let consumers know “where and how goods are made, and even to verify the authenticity of brand-name products.” 

"As electronic devices like cell phones become more sophisticated, they could potentially have the ability to read this kind of photonic labeling," Shtein said. "So I could imagine a future where woven-in labels are a useful feature for consumers as well as recyclers."

What we really need is to have fewer clothes to recycle in the first place; we need a cultural shift away from rapidly changing fashion trends and the cheap clothes that feed them. Yet we will likely always have tons of textiles landing in landfill. If weaving in a special fiber can help get textiles into a circular recycling system, then bring it on. As of now, the team has applied for patent protection and is analyzing paths forward to commercialize the technology.

The study, Polymeric photonic crystal fibers for textile tracing and sorting, was published in Advanced Materials Technologies.