Is this artificial silk super strong? That’s so metal.
Give revamped silkworm silk a metal bath The strands may be both strong and stiff.Scientists report October 6th Matter. The team discovered that some strands were as strong as silk spun by spiders.
This is the latest step in a long-running quest to produce fibers that are as strong, light and biodegradable like spider silk. The potential uses of this material range from biomedical to athletic if scientists can mass-produce it. Sutures, artificial ligaments and tendons — even sporting equipment could get an arachnid enhancement.
“If you’ve got a climbing rope that weighs half of what it normally does and still has the same mechanical properties, then obviously you’re going to be a happy climber,” says Randy Lewis, a silk scientist at Utah State University in Logan who was not involved with the study.
It was a challenge to find enough silky material for these strong products. Although silk from silkworms can be harvested easily, it is not very strong. It isn’t easy to find spider silk, which is considered the gold standard in handspun strength, toughness and durability. “Unlike silkworms, spiders cannot be farmed due to their territorial and aggressive nature,” write study coauthor Zhi Lin, a structural biologist at Tianjin University in China, and colleagues.
Researchers from all over the globe have attempted to spin strong strands in the laboratory using silkworm cocoons. The first step is to strip off the silk’s gummy outer coating. This can be done by boiling the fibers in water. However, this can lead to a gummy outer coating. If the proteins get too damaged, it’s hard for scientists to respin 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 gentler approaches, one of which used lower temperatures and a papaya enzyme, to help dissolve the silk’s coating. The mild-mannered method worked. “They don’t have little itty-bitty pieces of silk protein,” Lewis says. “That’s huge because the bigger the proteins that remain, the stronger the fibers are going to be.”
After completing some steps, researchers forced the silk sludge through the tube. It was like sucking toothpaste out of a tube. They then bathed the extruded Silk in a solution with zinc and iron ions. The strands were stretched like taffy to create long, thin fibers. The metal dip 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.
The team’s real innovation may be that “they’ve managed to unspin silk in a less damaging way,” Holland says. Lewis agrees. “In my mind,” he says, “that’s a major step forward.”
