Researchers are studying the way the brown recluse spider spins its webs to provide clues for developing stronger and lighter-weight materials, such as those that can be used in space and other applications.
A team from Virginia’s College of William & Mary and the University of Oxford in the United Kingdom have been observing the way the spider, a fearsome one known for its particularly powerful poison, creates extra-tough silk by the unique way it spins loops into each strand.
They are using this inspiration to consider how to make stronger textiles and other materials that also are light in weight, said Hannes Schniepp, an assistant professor of applied science at William & Mary.
“Rather than a cylindrical or round fiber, they make an extremely flat and thin ribbon,” he said. “We only found out while studying them that they have spinning apparatus that makes thousands of tiny loops into the silk. We then found out that these loops enhance the toughness of the material -- and that is exactly what we are always interested in: lightweight materials with outstanding mechanical properties.”
The team from both universities collaborated on a paper about their discoveries in the journal Materials Horizons, a publication of the Royal Society of Chemistry.
Brown recluse spiders don’t have the most cuddly reputation. They are extremely poisonous to humans; a bite from the venomous spider is extraordinarily painful and causes a person’s skin to become necrotic. However, despite the risk to humans— Schniepp joked that the team tries to “make sure we don’t get bitten” (and no one so far has)—the spider poses significant research value for materials scientists.
|Researchers at the College of William & Mary in Virginia are studying the way the brown recluse spider (pictured here in a lab at the college) spins its web to provide clues for developing stronger materials, such as those that can be used in space and other applications. The work is being done in conjunction with researchers at Oxford University. (Source: Joseph McClain, College of William & Mary)|
While most spiders spin webs to catch flying prey, the brown recluse does not spin what most people think of as a typical spider web. Its webs are concentric, spoked constructions that span sidewalks, putting them in the class of spiders known as orb weavers that aim to entangle ground-dwelling insect prey, according to researchers.
To observe the spiders safely, researchers kept them well secured in individual jars and used microscopes to get a closer look, he said.
“We use microscopes with different magnifications to study the spinning mechanism and the structure of the spun silk,” Schniepp said. “Since the spinneret of the recluse spider is so incredibly fast, we actually needed to connect a high-speed camera with our microscopes to capture more of the details.”
The team found several surprising and useful things in their observations, he said. First, the recluse spider has a fascinating spinneret totally unique among all spiders, with several moving parts, Schniepp said. “When it works, it looks a little bit like a microscopic sewing machine that periodically winds the silk into a looped structure,” he said.
Second, and perhaps most importantly, Schniepp said, researchers observed that these loops actually make the material tougher, which means that the material can absorb more energy before it breaks. This is what can be applied to other materials to give them the same properties, an idea with which the team experimented, he said.
“For instance, we took a simple piece of sticky tape, and just put one small loop into it,” Schniepp said. “When we stretched this sticky tape with the loop, we found that the toughness of this tape had already gone up by about 30 percent. This already demonstrates that the principle observed in the recluse silk on the microscale still works, even when carried out with much larger objects.”
The looping principle can be applied to a range of materials to increase their capability of absorbing energy, as well as to make brittle materials more ductile, he said. These are both characteristics that can be used in space applications, as well as others, Schniepp said.
“This could be used for carbon fibers, which tend to be very brittle,” he said. “We were thinking about making nets out of looped fibers with tremendous energy-absorbing capabilities to catch incoming objects with high energy or high velocity. Examples would be projectiles on Earth, and micrometeorites or space junk in orbit.
Researchers plan to continue their work to examine the spider silk with microscopes of the highest resolutions to find the molecular-scale origins for its “fantastic” strength and toughness, Schniepp said.
Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 15 years. She currently resides in a village on the southwest coast of Portugal.