Velvet worm slime: Reversible liquid-to-fiber transformation inspires sustainable materials

A new discovery about the slime ejected by velvet worms could revolutionize sustainable material design, according to a study by McGill University researchers. Their findings outline how a naturally occurring protein structure, conserved across species from Australia, Singapore and Barbados over nearly 400 million years of evolution, enables the slime's transformation from liquid to fiber and back again. It's a discovery that could inspire next-generation recyclable bioplastics.

"Nature has already figured out a way to make materials that are both strong and recyclable," said Matthew Harrington, a chemistry professor and Canada Research Chair in green chemistry, who led the study. "By decoding the molecular structure of velvet worm slime, we're now one step closer to replicating that efficiency for the materials we use every day."

Velvet worms, small caterpillar-like creatures found in humid forests of the southern hemisphere, use their slime to capture prey. When ejected, the slime rapidly hardens into fibers as strong as nylon. The slime dissolves in water and can be reconstituted into new fibers. Until now, the molecular mechanism behind this reversibility remained a mystery.

Using protein sequencing and AI-driven structure prediction (AlphaFold, the 2024 Nobel Prize-winning tool), Harrington's team identified previously unknown proteins in the slime that function similarly to cell receptors in the immune system. The researchers believe the receptor proteins function to link large structural proteins during fiber formation. By comparing two subgroups of velvet worms that separated nearly 380 million years ago, the researchers demonstrated the evolutionary significance and functional relevance of this protein.

The research is published in the journal Proceedings of the National Academy of Sciences.

A blueprint for recyclable materials

Traditional plastics and synthetic fibers are typically made using petroleum-based precursors and require energy-intensive processes to manufacture and recycle, often involving heat or chemical treatments. The velvet worm, however, uses simple mechanical forces—pulling and stretching—to generate strong, durable fibers from biorenewable precursors, which can later be dissolved and reused without harmful byproducts.

"Obviously, a plastic bottle that dissolves in water would have limited use, but by adjusting the chemistry of this binding mechanism, we can get around this issue," said Harrington.

The study was co-authored by researchers from McGill University and Nanyang Technological University (NTU) in Singapore. The team's next challenge will be to experimentally verify the binding interactions and explore whether the principle can be adapted for engineered materials.