A team led by Professor Dong Soo Hwang (Division of Environmental Science and Engineering / Division of interdisciplinary bioscience & bioengineering, POSTECH) and Professor Jimin Choi (Environmental Research Institute) recreated a golden fiber similar to sea silk using the pen shell (Atrina pectinata), a shellfish cultivated in Korean coastal waters. Their findings, published in Advanced Materials, not only revive an ancient textile but also explain why its golden appearance remains vibrant over time.

The Rise and Fall of Legendary Sea Silk

Often called the "golden fiber of the sea," sea silk was highly prized during the Roman era. The material was made from byssus threads produced by Pinna nobilis, a large Mediterranean clam that uses these fibers to anchor itself to rocky surfaces.

Sea silk became famous for its shimmering golden color, light weight, and exceptional durability. Its rarity and beauty earned it a near mythical reputation. One of the most well known examples is the Holy Face of Manoppello, a religious relic preserved in Italy for centuries that is believed to have been made from sea silk.

In recent decades, however, marine pollution and environmental decline have pushed Pinna nobilis toward extinction. The species is now endangered, and the European Union has completely banned its harvesting. As a result, authentic sea silk has become extraordinarily rare and is produced only in tiny amounts by a small number of artisans.

Recreating an Ancient Fiber

To find an alternative source, the POSTECH researchers investigated the pen shell Atrina pectinata, which is already farmed for food in Korean waters.

Like Pinna nobilis, the pen shell produces byssus threads that help it attach to surfaces. The team discovered that these fibers closely resemble those of the Mediterranean clam both physically and chemically. Using this similarity as a starting point, they developed a method for processing pen shell byssus into a material that recreates the appearance of ancient sea silk.

But recreating the fiber was only part of the achievement.

The Secret Behind Sea Silk's Golden Glow

The researchers also uncovered the mechanism responsible for sea silk's distinctive golden color and its remarkable resistance to fading.

Rather than coming from dyes, the color is created through structural coloration, a phenomenon in which microscopic structures interact with light to produce color. The team found that sea silk's iridescent appearance comes from layered spherical protein structures known as "photonin."

These structures reflect and manipulate light in much the same way that soap bubbles or butterfly wings create vibrant colors. Because the effect is produced by the material's structure rather than added pigments, the color remains highly stable over long periods.

The researchers also found that the more precisely these proteins are organized, the stronger and more vivid the color becomes. Unlike conventional textiles, where color is applied through dyeing, sea silk generates its golden hue from the arrangement of proteins within the fiber itself. This helps explain how the material can retain its brilliance for centuries.

Sustainable Textiles From Marine Waste

The work could have implications far beyond recreating a historical luxury fabric.

The byssus fibers of pen shells have traditionally been discarded as waste. By converting them into a valuable textile, the researchers demonstrated a way to reduce marine waste while creating sustainable materials with cultural and historical significance.

Professor Dong Soo 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."