Spiders are incredible web creators, and researchers are learning more about their impressively strong and elastic silk threads.
Spiders are nature’s artists, spinning intricate webs to capture prey or even convey messages, as depicted in the children’s book Charlotte’s Web. These threads combine exceptional strength and elasticity.
In polymer materials, these properties are often difficult to achieve simultaneously, as increased elasticity can come at the expense of strength. This challenge motivated researchers from the University of Greifswald to investigate the properties of spider silk from netcasting spiders, seeking new insights that could inform the design of synthetic materials—taking a page, or rather a thread, from these arachnids to improve both strength and elasticity.
In a recent study, published in the Proceedings of the National Academy of Sciences, the team found that the architecture of the netcaster’s thread is like a bungee cable core surrounded by looped bundles of fine fibers that can stiffen and enhance load-bearing capacity when capturing prey.1 Thus, researchers may draw inspiration from the spider’s unique thread-production process to design improved synthetic materials.
The netcasting spiders, as their name aptly suggests, propel a web towards their prey. As it flies through the air, the web undergoes significant, yet reversible, deformation. This thread can sustain elongations over 150 percent; a staggering amount compared to orb-weaver spiders whose silk can fracture at elongations over 20 percent.
The researchers used high-speed videography to assess the tensile properties of the web at different sections. As various parts of the web expand and contract, distinct regions experience differing levels of strain. They found that spiders create a gradient of stiffness along the thread through a reel-spinning technique.
Closer examination using polarized light microscopy and field-emission scanning electron microscopy revealed that each thread consists of an elastomeric core fiber surrounded by loops of silk fibers. These looped fibers varied in density, imparting strong, stiff properties in load-bearing regions and softer, hyperelastic behavior in other areas.
Although further research is needed to fully elucidate the mix of silk threads that contribute to web performance, these insights into looped fiber-reinforced cores may inspire the design of synthetic materials that require both high strength and elasticity.
