[Image above] Credit: uditha wickramanayaka; Flickr CC BY NC 2.0
Spiders’ outward creepiness is a matter of personal opinion—but we can all agree they’re fascinating creatures.
In the field of materials science, researchers continue to develop cost-efficient, practical methods for creating spider silk thread in the lab that rivals the impressive strength and durability of the real thing. Because extracting natural spider silk from the source is far from scalable.
Scientists at Bolt Threads in Emeryville, Calif., have made strides in their work to develop a scalable way to create synthetic spider silk-like fibers by fermenting spider silk proteins from bioengineered yeast.
Japanese company Spiber is also on the bandwagon, partnering with high-performance sportswear outfitter The North Face to create a parka made from genetically engineered spider silk fiber.
Spider silk could revolutionize materials used for things like bulletproof vests, biodegradable water bottles, flexible bridge suspension ropes, vehicle air bags, and protective cases and covers for electronics, which all rely on unparalleled toughness and flexibility when put to the test.
As some researchers work toward perfecting a synthetic, scalable spider silk solution, others are looking closely at the actual composition of spider web threads—specifically “signal threads.”
Beth Mortimer from the Oxford Silk Group, based in the Department of Zoology at the University of Oxford in England, and her colleagues are studying spiders’ signal threads—the threads in the web that spiders use to monitor when they’ve caught new prey.
In an interview with Oxford University’s Science Blog, Mortimer says that although signal threads are “likely made of the same material of other radial threads in the web, the signal threads are the last part of the web to be built.” Spiders use the signal thread to transmit vibrations from prey caught in the web and also as a “tightrope” so the spider can move quickly from it’s place on the web’s perimeter to the capture.
(Check out this video from the University of Oxford that shows a spider rebuilding her signal thread!)
Credit: Oxford University; YouTube
Mortimer and her team examined the signal threads’ structure, which gives insight into the their multipurpose functions.
“Firstly, the signal thread structure is surprisingly variable: while some had only four fibers in their signal thread rope, others had up to 16 fibers. The number of fibers and the load-bearing capacity of the signal threads varied with the movement of the spiders—each time they ran from the retreat to the hub, more silk fibers were added to the signal thread, which was then able to sustain more weight,” Mortimer tells Oxford’s Science Blog.
And, Mortimer says, the spider carefully controls this variable structure for specific purposes.
“As more fibers are added to the signal thread, the spider carefully tensions each one to simultaneously increase the overall tension of the signal thread. This is important, as the vibrational properties of the signal thread remain constant across many different signal thread sizes… These fibers closely interact with each other to form a signal thread that behaves as one unit, which gives a comparatively simple vibration signal to the spider,” Mortimer explains.
So what does this study mean for potential commercial applications when it comes to leveraging the science behind signal threads? Mortimer says this knowledge could lead to advances in remote sensing technologies where passive monitoring is used or in smaller-scale systems used for harvesting energy, for starters.
“The signal thread structure enables consistent signaling across a range of cable sizes, so it could be employed in contexts where passive monitoring is required. And the system would be well suited to active sensing of vibrations—the combination of the signal thread’s structure and piezoelectric coatings could provide new systems for small-scale energy harvesting, where vibrations could be turned into electricity,” Mortimer says.
Opportunities aren’t limited to micro-electronic mechanical systems, however, and also extend to larger-scale applications. “The variability of the natural system therefore gives insights into how this simple system can be tuned for a range of different size scales,” Mortimer says.
The study, published in the Journal of the Royal Society Interface, is “Unpicking the signal thread of the sector web spider Zygiella x-notata” (DOI: 10.1098/rsif.2015.0633).