A legendary fabric that was once reserved for emperors has been recreated from clam waste by a team of Korean researchers.
Sea silk, also known as the “golden fiber of the sea”, was one of the most valued materials in ancient Rome, typically used by individuals in high authority. This silk is made from the byssus threads secreted by Pinna nobilis, a large clam native to the Mediterranean, which uses its exceptional threads to anchor itself to rocks. Sea silk has earned the name of “legendary silk” for its shimmering and unfading color and its extraordinary durability. However, due to ecological decline, the species was declared endangered in 2019 and with that, the European Union has banned its harvesting.
With the endangerment of Pinna nobilis, the POSTECH research team in Korea turned their attention to Atrina pectinata, a closely related clam species in which its threads shared physical and chemical similarities to those of Pinna nobilis. As well as this, A. pectinata is found abundantly in Korea, as it is commonly used for food. The byssus of A. pectinata is usually discarded as waste, so the researchers were able to use them to recreate golden threads that were indistinguishable from those of P. nobilis.
Another stunning characteristic of A. pectinata threads is its golden hue and resistance to fading over time. Unlike animal-based fibers such as wool and silk that are made from long, fibrous proteins, the team found that sea silk is primarily composed of spherical proteins called photonins. These spherical proteins assemble into nanofibrils that twist together in helical bundles. The proteins form layered arrangements that interact with light which gives these threads their amazing shine. Since the color of the thread comes from this highly stable structure and not from any type of pigment, the color “doesn’t fade for more than 1,000 years,” said Jimin Choi, a biological engineer at the Pohang University of Science and Technology in Korea.
Globular proteins are typically unstable, says Professor Doo Soo Hwang from the Pohang University of Science and Technology. However, in sea silk, the photonins are reinforced by a mesh of sugars and matrix proteins which provide strength and durability. The researchers noted that the more ordered the protein structure is within the fibers, the better the structural color becomes. These findings could help to revive sea silk production without contributing to the endangerment of A. pectinata, mainly due to its large consumption in Korea. As well as this, the findings in regards to the thread color could help to engineer nontoxic golden pigments to be used in textiles and cosmetics.
Professor Hwang noted, “Structurally colored textiles are inherently resistant to fading. Our technology enables long-lasting color without the use of dyes or metals, opening new possibilities for sustainable fashion and advanced materials.”
