Super strong artificial silk? It’s so metal.
Giving revamped silkworm silk a metallic bath can make strands both strong and stiffscientists report on October 6 to Question. Some strands were up to 70% stronger than spider-spun silk, the team found.
This work is the latest in a decades-long quest to create fibers as strong, light and biodegradable as spider silk. If scientists could mass-produce such material, the potential uses range from biomedical to athletics. Artificial sutures, ligaments and tendons – even sports equipment could benefit from arachnid enhancement.
“If you have a climbing rope that weighs half of what it normally does and still has the same mechanical properties, then obviously you’ll be a happy climber,” says Randy Lewis, a silk specialist at the university. of Utah State in Logan who did not participate in the study.
Finding enough silky material to make these super tough products was a big hurdle. Silkworm silk is easy to harvest, but not very strong. And spider silk, the benchmark for toughness and tenacity, isn’t exactly easy to collect. “Unlike silkworms, spiders cannot be cultured due to their territorial and aggressive nature,” write study co-author Zhi Lin, a structural biologist at Tianjin University in China, and colleagues. .
Scientists around the world have tried spinning strong strands in the lab using silkworm cocoons as a starting point. The first step is to remove the gummy outer coating from the silk. Scientists can do this by boiling the fibers in a chemical bath, but it can be like giving silk proteins a hatchet. If the proteins are too damaged, it’s difficult for scientists to turn them into high-quality strands, says Chris Holland, a materials scientist at the University of Sheffield in England who was not involved in the study.
Lin’s team tried milder approaches, one of which used lower temperatures and a papaya enzyme, to help dissolve the silk coating. This mild-mannered method seemed to work. “They don’t have little bits of silk protein,” Lewis says. “That’s huge because the bigger the protein that’s left, the stronger the fiber is going to be.”
After a few processing steps, the researchers forced the resulting silk mud through a small tube, like squeezing toothpaste. Then they bathed the extruded silk in a solution containing zinc and iron ions, eventually stretching the strands like taffy into long, thin fibers. The soaking of the metal could be why some of the strands were so strong – Lin’s team detected zinc ions in the finished fibers. But Holland and Lewis aren’t so sure.
Perhaps the team’s real innovation was that “they were able to unravel the silk in a less damaging way,” says Holland. Lewis agrees. “In my mind,” he said, “that’s a big step forward.”