Spiders use their hind legs to pull silk threads, strengthening them and making webs more durable. Northwestern researchers discovered that stretching aligns protein chains and forms more bonds, resulting in tougher silk.
Lab tests confirmed this, offering the potential for creating stronger materials like biodegradable sutures and protective armor.
McCormick School of Engineering’s Sinan Keten, the study’s senior author, said, “Researchers already knew this stretching, or drawing, is necessary for making strong fibers. But no one necessarily knew why. With our computational method, we were able to probe what’s happening at the nanoscale to gain insights that cannot be seen experimentally. We could examine how drawing relates to the silk’s mechanical properties.”
Northwestern Jacob Graham, the study’s first author, said, “Spiders perform the drawing process naturally; when they spin silk out of their silk gland, spiders use their hind legs to grab the fiber and pull it out. That stretches the fiber as it’s being formed. It makes the fiber very strong and very elastic. We found that you can modify the fiber’s mechanical properties simply by modifying the amount of stretching.”
Green Method Developed For Making Artificial Spider Silk
Spider silk is stronger than steel, tougher than Kevlar, and stretchier than rubber. Farming spiders for silk is challenging and inefficient, so scientists are recreating silk-like materials in labs.
Spider silk, known as the strongest organic fiber, is biodegradable, making it perfect for medical uses like sutures and wound-closure gels that safely break down in the body.
Professor Fuzhong Zhang has been engineering microbes to produce spider-silk proteins at Washington University in St. Louis.
By extruding and hand-stretching these proteins, his team has created artificial fibers resembling the strong threads spun by the golden silk orb weaver spider. This approach could revolutionize the development of durable, sustainable materials for medical and other applications.
Although researchers have created a “recipe” for artificial spider silk, the mechanics of how spinning enhances its strength remain unclear. To address this, Keten and Graham developed a computational model to study Zhang’s artificial silk at the molecular level.
Simulations showed that stretching aligns protein chains and increases hydrogen bonds, which act like tiny bridges between them. These changes enhance the silk’s strength, elasticity, and toughness. Stretching the fibers up to six times their original length turns weak silk into incredibly strong material.
The team used spectroscopy and tensile testing on real fibers from the WashU group to confirm their findings. The results matched their predictions: stretching the fibers turned spherical protein globs into interconnected networks. This alignment made the fibers tougher, with bundled proteins unraveling more before breaking, while already extended proteins required more force to snap.
Interestingly, researcher Graham admitted he once saw spiders as mere nuisances but now views them with admiration. Engineered spider silk, offering a strong and biodegradable alternative to synthetic plastics, underscores the potential of these creatures to inspire real-world solutions.
Journal Reference:
Jacob Graham, Shri Subramani, Xinyan Yang, et al. Charting the envelope of mechanical properties of synthetic silk fibers through predictive modeling of the drawing process. Science Advances. DOI: 10.1126/sciadv.adr3833