Tag Archives: spiderwebs

Spiders can outsource hearing to their webs

A March 29, 2022 news item on ScienceDaily highlights research into how spiders hear,

Everyone knows that humans and most other vertebrate species hear using eardrums that turn soundwave pressure into signals for our brains. But what about smaller animals like insects and arthropods? Can they detect sounds? And if so, how?

Distinguished Professor Ron Miles, a Department of Mechanical Engineering faculty member at Binghamton University’s Thomas J. Watson College of Engineering and Applied Science, has been exploring that question for more than three decades, in a quest to revolutionize microphone technology.

A newly published study of orb-weaving spiders — the species featured in the classic children’s book “Charlotte’s Web” — has yielded some extraordinary results: The spiders are using their webs as extended auditory arrays to capture sounds, possibly giving spiders advanced warning of incoming prey or predators.

Binghamton University (formal name: State University of New York at Binghamton) has made this fascinating (to me anyway) video available,

Binghamton University and Cornell University (also in New York state) researchers worked collaboratively on this project. Consequently, there are two news releases and there is some redundancy but I always find that information repeated in different ways is helpful for learning.

A March 29, 2022 Binghamton University news release (also on EurekAlert) by Chris Kocher gives more detail about the work (Note: Links have been removed),

It is well-known that spiders respond when something vibrates their webs, such as potential prey. In these new experiments, researchers for the first time show that spiders turned, crouched or flattened out in response to sounds in the air.

The study is the latest collaboration between Miles and Ron Hoy, a biology professor from Cornell, and it has implications for designing extremely sensitive bio-inspired microphones for use in hearing aids and cell phone

Jian Zhou, who earned his PhD in Miles’ lab and is doing postdoctoral research at the Argonne National Laboratory, and Junpeng Lai, a current PhD student in Miles’ lab, are co-first authors. Miles, Hoy and Associate Professor Carol I. Miles from the Harpur College of Arts and Sciences’ Department of Biological Sciences at Binghamton are also authors for this study. Grants from the National Institutes of Health to Ron Miles funded the research.

A single strand of spider silk is so thin and sensitive that it can detect the movement of vibrating air particles that make up a soundwave, which is different from how eardrums work. Ron Miles’ previous research has led to the invention of novel microphone designs that are based on hearing in insects.

“The spider is really a natural demonstration that this is a viable way to sense sound using viscous forces in the air on thin fibers,” he said. “If it works in nature, maybe we should have a closer look at it.”

Spiders can detect miniscule movements and vibrations through sensory organs on their tarsal claws at the tips of their legs, which they use to grasp their webs. Orb-weaver spiders are known to make large webs, creating a kind of acoustic antennae with a sound-sensitive surface area that is up to 10,000 times greater than the spider itself.

In the study, the researchers used Binghamton University’s anechoic chamber, a completely soundproof room under the Innovative Technologies Complex. Collecting orb-weavers from windows around campus, they had the spiders spin a web inside a rectangular frame so they could position it where they wanted.

The team began by using pure tone sound 3 meters away at different sound levels to see if the spiders responded or not. Surprisingly, they found spiders can respond to sound levels as low as 68 decibels. For louder sound, they found even more types of behaviors.

They then placed the sound source at a 45-degree angle, to see if the spiders behaved differently. They found that not only are the spiders localizing the sound source, but they can tell the sound incoming direction with 100% accuracy.

To better understand the spider-hearing mechanism, the researchers used laser vibrometry and measured over one thousand locations on a natural spider web, with the spider sitting in the center under the sound field. The result showed that the web moves with sound almost at maximum physical efficiency across an ultra-wide frequency range.

“Of course, the real question is, if the web is moving like that, does the spider hear using it?” Miles said. “That’s a hard question to answer.”

Lai added: “There could even be a hidden ear within the spider body that we don’t know about.”

So the team placed a mini-speaker 5 centimeters away from the center of the web where the spider sits, and 2 millimeters away from the web plane — close but not touching the web. This allows the sound to travel to the spider both through air and through the web. The researchers found that the soundwave from the mini-speaker died out significantly as it traveled through the air, but it propagated readily through the web with little attenuation. The sound level was still at around 68 decibels when it reached the spider. The behavior data showed that four out of 12 spiders responded to this web-borne signal.

Those reactions proved that the spiders could hear through the webs, and Lai was thrilled when that happened: “I’ve been working on this research for five years. That’s a long time, and it’s great to see all these efforts will become something that everybody can read.”

The researchers also found that, by crouching and stretching, spiders may be changing the tension of the silk strands, thereby tuning them to pick up different frequencies. By using this external structure to hear, the spider could be able to customize it to hear different sorts of sounds.

Future experiments may investigate how spiders make use of the sound they can detect using their web. Additionally, the team would like to test whether other types of web-weaving spiders also use their silk to outsource their hearing.

“It’s reasonable to guess that a similar spider on a similar web would respond in a similar way,” Ron Miles said. “But we can’t draw any conclusions about that, since we tested a certain kind of spider that happens to be pretty common.”

Lai admitted he had no idea he would be working with spiders when he came to Binghamton as a mechanical engineering PhD student.

“I’ve been afraid of spiders all my life, because of their alien looks and hairy legs!” he said with a laugh. “But the more I worked with spiders, the more amazing I found them. I’m really starting to appreciate them.”

A March 29, 2022 Cornell University news release (also on EurekAlert but published March 30, 2022) by Krishna Ramanujan offers a somewhat different perspective on the work, Note: Links have been removed)

Charlotte’s web is made for more than just trapping prey.

A study of orb weaver spiders finds their massive webs also act as auditory arrays that capture sounds, possibly giving spiders advanced warning of incoming prey or predators.

In experiments, the researchers found the spiders turned, crouched or flattened out in response to sounds, behaviors that spiders have been known to exhibit when something vibrates their webs.

The paper, “Outsourced Hearing in an Orb-weaving Spider That Uses its Web as an Auditory Sensor,” published March 29 [2022] in the Proceedings of the National Academy of Sciences, provides the first behavioral evidence that a spider can outsource hearing to its web.

The findings have implications for designing bio-inspired extremely sensitive microphones for use in hearing aids and cell phones.

A single strand of spider silk is so thin and sensitive it can detect the movement of vibrating air particles that make up a sound wave. This is different from how ear drums work, by sensing pressure from sound waves; spider silk detects sound from nanoscale air particles that become excited from sound waves.

“The individual [silk] strands are so thin that they’re essentially wafting with the air itself, jostled around by the local air molecules,” said Ron Hoy, the Merksamer Professor of Biological Science, Emeritus, in the College of Arts and Sciences and one of the paper’s senior authors, along with Ronald Miles, professor of mechanical engineering at Binghamton University.

Spiders can detect miniscule movements and vibrations via sensory organs in their tarsi – claws at the tips of their legs they use to grasp their webs, Hoy said. Orb weaver spiders are known to make large webs, creating a kind of acoustic antennae with a sound-sensitive surface area that is up to 10,000 times greater than the spider itself.

In the study, the researchers used a special quiet room without vibrations or air flows at Binghamton University. They had an orb-weaver build a web inside a rectangular frame, so they could position it where they wanted. The team began by putting a mini-speaker within millimeters of the web without actually touching it, where sound operates as a mechanical vibration. They found the spider detected the mechanical vibration and moved in response.

They then placed a large speaker 3 meters away on the other side of the room from the frame with the web and spider, beyond the range where mechanical vibration could affect the web. A laser vibrometer was able to show the vibrations of the web from excited air particles.

The team then placed the speaker in different locations, to the right, left and center with respect to the frame. They found that the spider not only detected the sound, it turned in the direction of the speaker when it was moved. Also, it behaved differently based on the volume, by crouching or flattening out.

Future experiments may investigate whether spiders rebuild their webs, sometimes daily, in part to alter their acoustic capabilities, by varying a web’s geometry or where it is anchored. Also, by crouching and stretching, spiders may be changing the tension of the silk strands, thereby tuning them to pick up different frequencies, Hoy said.

Additionally, the team would like to test if other types of web-weaving spiders also use their silk to outsource their hearing. “The potential is there,” Hoy said.

Miles’ lab is using tiny fiber strands bio-inspired by spider silk to design highly sensitive microphones that – unlike conventional pressure-based microphones – pick up all frequencies and cancel out background noise, a boon for hearing aids.  

Here’s a link to and a citation for the paper,

Outsourced hearing in an orb-weaving spider that uses its web as an auditory sensor by Jian Zhou, Junpeng Lai, Gil Menda, Jay A. Stafstrom, Carol I. Miles, Ronald R. Hoy, and Ronald N. Miles. Proceedings of the National Academy of Sciences (PNAS) DOI: https://doi.org/10.1073/pnas.2122789119 Published March 29, 2022 | 119 (14) e2122789119

This paper appears to be open access and video/audio files are included (you can heat the sound and watch the spider respond).

One of world’s most precise microchip sensors thanks to nanotechnology, machine learning, extended cognition, and spiderwebs

I love science stories about the inspirational qualities of spiderwebs. A November 26, 2021 news item on phys.org describes how spiderwebs have inspired advances in sensors and, potentially, quantum computing,,

A team of researchers from TU Delft [Delft University of Technology; Netherlands] managed to design one of the world’s most precise microchip sensors. The device can function at room temperature—a ‘holy grail’ for quantum technologies and sensing. Combining nanotechnology and machine learning inspired by nature’s spiderwebs, they were able to make a nanomechanical sensor vibrate in extreme isolation from everyday noise. This breakthrough, published in the Advanced Materials Rising Stars Issue, has implications for the study of gravity and dark matter as well as the fields of quantum internet, navigation and sensing.

Inspired by nature’s spider webs and guided by machine learning, Richard Norte (left) and Miguel Bessa (right) demonstrate a new type of sensor in the lab. [Photography: Frank Auperlé]

A November 24, 2021 TU Delft press release (also on EurekAlert but published on November 23, 2021), which originated the news item, describes the research in more detail,

One of the biggest challenges for studying vibrating objects at the smallest scale, like those used in sensors or quantum hardware, is how to keep ambient thermal noise from interacting with their fragile states. Quantum hardware for example is usually kept at near absolute zero (−273.15°C) temperatures, with refrigerators costing half a million euros apiece. Researchers from TU Delft created a web-shaped microchip sensor which resonates extremely well in isolation from room temperature noise. Among other applications, their discovery will make building quantum devices much more affordable.

Hitchhiking on evolution
Richard Norte and Miguel Bessa, who led the research, were looking for new ways to combine nanotechnology and machine learning. How did they come up with the idea to use spiderwebs as a model? Richard Norte: “I’ve been doing this work already for a decade when during lockdown, I noticed a lot of spiderwebs on my terrace. I realised spiderwebs are really good vibration detectors, in that they want to measure vibrations inside the web to find their prey, but not outside of it, like wind through a tree. So why not hitchhike on millions of years of evolution and use a spiderweb as an initial model for an ultra-sensitive device?” 

Since the team did not know anything about spiderwebs’ complexities, they let machine learning guide the discovery process. Miguel Bessa: “We knew that the experiments and simulations were costly and time-consuming, so with my group we decided to use an algorithm called Bayesian optimization, to find a good design using few attempts.” Dongil Shin, co-first author in this work, then implemented the computer model and applied the machine learning algorithm to find the new device design. 

Microchip sensor based on spiderwebs
To the researcher’s surprise, the algorithm proposed a relatively simple spiderweb out of 150 different spiderweb designs, which consists of only six strings put together in a deceivingly simple way. Bessa: “Dongil’s computer simulations showed that this device could work at room temperature, in which atoms vibrate a lot, but still have an incredibly low amount of energy leaking in from the environment – a higher Quality factor in other words. With machine learning and optimization we managed to adapt Richard’s spider web concept towards this much better quality factor.”

Based on this new design, co-first author Andrea Cupertino built a microchip sensor with an ultra-thin, nanometre-thick film of ceramic material called Silicon Nitride. They tested the model by forcefully vibrating the microchip ‘web’ and measuring the time it takes for the vibrations to stop. The result was spectacular: a record-breaking isolated vibration at room temperature. Norte: “We found almost no energy loss outside of our microchip web: the vibrations move in a circle on the inside and don’t touch the outside. This is somewhat like giving someone a single push on a swing, and having them swing on for nearly a century without stopping.”

Implications for fundamental and applied sciences
With their spiderweb-based sensor, the researchers’ show how this interdisciplinary strategy opens a path to new breakthroughs in science, by combining bio-inspired designs, machine learning and nanotechnology. This novel paradigm has interesting implications for quantum internet, sensing, microchip technologies and fundamental physics: exploring ultra-small forces for example, like gravity or dark matter which are notoriously difficult to measure. According to the researchers, the discovery would not have been possible without the university’s Cohesion grant, which led to this collaboration between nanotechnology and machine learning.

Here’s a link to and a citation for the paper,

Spiderweb Nanomechanical Resonators via Bayesian Optimization: Inspired by Nature and Guided by Machine Learning by Dongil Shin, Andrea Cupertino, Matthijs H. J. de Jong, Peter G. Steeneken, Miguel A. Bessa, Richard A. Norte. Advanced Materials Volume34, Issue3 January 20, 2022 2106248 DOI: https://doi.org/10.1002/adma.202106248 First published (online): 25 October 2021

This paper is open access.

If spiderwebs can be sensors, can they also think?

it’s called ‘extended cognition’ or ‘extended mind thesis’ (Wikipedia entry) and the theory holds that the mind is not solely in the brain or even in the body. Predictably, the theory has both its supporters and critics as noted in Joshua Sokol’s article “The Thoughts of a Spiderweb” originally published on May 22, 2017 in Quanta Magazine (Note: Links have been removed),

Millions of years ago, a few spiders abandoned the kind of round webs that the word “spiderweb” calls to mind and started to focus on a new strategy. Before, they would wait for prey to become ensnared in their webs and then walk out to retrieve it. Then they began building horizontal nets to use as a fishing platform. Now their modern descendants, the cobweb spiders, dangle sticky threads below, wait until insects walk by and get snagged, and reel their unlucky victims in.

In 2008, the researcher Hilton Japyassú prompted 12 species of orb spiders collected from all over Brazil to go through this transition again. He waited until the spiders wove an ordinary web. Then he snipped its threads so that the silk drooped to where crickets wandered below. When a cricket got hooked, not all the orb spiders could fully pull it up, as a cobweb spider does. But some could, and all at least began to reel it in with their two front legs.

Their ability to recapitulate the ancient spiders’ innovation got Japyassú, a biologist at the Federal University of Bahia in Brazil, thinking. When the spider was confronted with a problem to solve that it might not have seen before, how did it figure out what to do? “Where is this information?” he said. “Where is it? Is it in her head, or does this information emerge during the interaction with the altered web?”

In February [2017], Japyassú and Kevin Laland, an evolutionary biologist at the University of Saint Andrews, proposed a bold answer to the question. They argued in a review paper, published in the journal Animal Cognition, that a spider’s web is at least an adjustable part of its sensory apparatus, and at most an extension of the spider’s cognitive system.

This would make the web a model example of extended cognition, an idea first proposed by the philosophers Andy Clark and David Chalmers in 1998 to apply to human thought. In accounts of extended cognition, processes like checking a grocery list or rearranging Scrabble tiles in a tray are close enough to memory-retrieval or problem-solving tasks that happen entirely inside the brain that proponents argue they are actually part of a single, larger, “extended” mind.

Among philosophers of mind, that idea has racked up citations, including supporters and critics. And by its very design, Japyassú’s paper, which aims to export extended cognition as a testable idea to the field of animal behavior, is already stirring up antibodies among scientists. …

It seems there is no definitive answer to the question of whether there is an ‘extended mind’ but it’s an intriguing question made (in my opinion) even more so with the spiderweb-inspired sensors from TU Delft.

Music on the web, a spider’s web, that is

I was expecting to see Markus Buehler and MIT (Massachusetts Institute of Technology) mentioned in this latest work on spiderwebs and music. Surprise! This latest research is from three universities in the UK as per a June 3, 2014 news item on ScienceDaily,

Spider silk transmits vibrations across a wide range of frequencies so that, when plucked like a guitar string, its sound carries information about prey, mates, and even the structural integrity of a web.

The discovery was made by researchers from the Universities of Oxford, Strathclyde, and Sheffield who fired bullets and lasers at spider silk to study how it vibrates. They found that, uniquely, when compared to other materials, spider silk can be tuned to a wide range of harmonics. The findings, to be reported in the journal Advanced Materials, not only reveal more about spiders but could also inspire a wide range of new technologies, such as tiny light-weight sensors.

A June 3, 2014 University of Oxford news release (also on EurekAlert), which originated the news item, explains the research and describes how it was conducted (firing bullets?),

‘Most spiders have poor eyesight and rely almost exclusively on the vibration of the silk in their web for sensory information,’ said Beth Mortimer of the Oxford Silk Group at Oxford University, who led the research. ‘The sound of silk can tell them what type of meal is entangled in their net and about the intentions and quality of a prospective mate. By plucking the silk like a guitar string and listening to the ‘echoes’ the spider can also assess the condition of its web.’

‘Most spiders have poor eyesight and rely almost exclusively on the vibration of the silk in their web for sensory information,’ said Beth Mortimer of the Oxford Silk Group at Oxford University, who led the research. ‘The sound of silk can tell them what type of meal is entangled in their net and about the intentions and quality of a prospective mate. By plucking the silk like a guitar string and listening to the ‘echoes’ the spider can also assess the condition of its web.’

This quality is used by the spider in its web by ‘tuning’ the silk: controlling and adjusting both the inherent properties of the silk, and the tensions and interconnectivities of the silk threads that make up the web. To study the sonic properties of the spider’s gossamer threads the researchers used ultra-high-speed cameras to film the threads as they responded to the impact of bullets. [emphasis mine] In addition, lasers were used to make detailed measurements of even the smallest vibration.

‘The fact that spiders can receive these nanometre vibrations with organs on each of their legs, called slit sensillae, really exemplifies the impact of our research about silk properties found in our study,’ said Dr Shira Gordon of the University of Strathclyde, an author involved in this research.

‘These findings further demonstrate the outstanding properties of many spider silks that are able to combine exceptional toughness with the ability to transfer delicate information,’ said Professor Fritz Vollrath of the Oxford Silk Group at Oxford University, an author of the paper. ‘These are traits that would be very useful in light-weight engineering and might lead to novel, built-in ‘intelligent’ sensors and actuators.’

Dr Chris Holland of the University of Sheffield, an author of the paper, said: ‘Spider silks are well known for their impressive mechanical properties, but the vibrational properties have been relatively overlooked and now we find that they are also an awesome communication tool. Yet again spiders continue to impress us in more ways than we can imagine.’

Beth Mortimer said: ‘It may even be that spiders set out to make a web that ‘sounds right’ as its sonic properties are intimately related to factors such as strength and flexibility.’

The research paper has not yet been published in Advanced Materials (I checked this morning, June 4, 2014).

However, there is this video from the researchers,

As for Markus Buehler’s work at MIT, you can find out more in my Nov. 28, 2012 posting, Producing stronger silk musically.

Bedbugs: a bean-based solution from the Balkans or an artificial spider web solution from Fibertrap

Today (Apr. 10, 2013), I came across two news items about ridding oneself of bedbugs. Given the amount of coverage the pests and their growing ubiquity have been receiving the last few years, it seems that at some point everyone will experience an infestation. So, it’s good to see that scientists and entrepreneurs are working on solutions.

First up, there’s a team of scientists who are studying how people in the Balkans rid themselves of bedbugs, from the Apr. 9, 2013 news item on ScienceDaily,

Inspired by a traditional Balkan bedbug remedy, researchers have documented how microscopic hairs on kidney bean leaves effectively stab and trap the biting insects, according to findings published online today [Apr. 9, 2013] in the Journal of the Royal Society Interface. Scientists at UC [University of California] Irvine and the University of Kentucky are now developing materials that mimic the geometry of the leaves.

I knew they were a problem but I hadn’t realized how very hardy the bugs are, from the news item,

Bedbugs have made a dramatic comeback in the U.S. in recent years, infesting everything from homes and hotels to schools, movie theaters and hospitals. Although not known to transmit disease, their bites can cause burning, itching, swelling and psychological distress. It helps to catch infestations early, but the nocturnal parasites’ ability to hide almost anywhere, breed rapidly and “hitchhike” from place to place makes detection difficult. They can survive as long as a year without a blood meal.

Current commercial prevention methods, including freezing, extreme heating, vacuuming and pesticides, can be costly and unreliable. Many sufferers resort to ineffective, potentially dangerous measures, such as spraying nonapproved insecticides themselves rather than hiring a professional.

The University of California Irvine Apr. 9, 2013 news release, which originated the news item, describes the researchers’ [Doctoral student Megan Szyndler, entomologist Catherine Loudon and chemist Robert Corn of UC Irvine and entomologists Kenneth Haynes and Michael Potter of the University of Kentucky] inspiration, the bean leaves, at more length and the proposed bedbug solution,

Their work was motivated by a centuries-old remedy for bedbugs used in Bulgaria, Serbia and other southeast European countries. Kidney bean leaves were strewn on the floor next to beds and seemed to ensnare the blood-seeking parasites on their nightly forays. The bug-encrusted greenery was burned the next morning to exterminate the insects.

Through painstaking detective work, the scientists discovered that the creatures are trapped within seconds of stepping on a leaf, their legs impaled by microscopic hooked hairs known botanically as trichomes.

Using the bean leaves as templates, the researchers have microfabricated materials that closely resemble them geometrically. The synthetic surfaces snag the bedbugs temporarily but do not yet stop them as effectively as real leaves, Loudon said, suggesting that crucial mechanics of the trichomes still need to be determined.

Theoretically, bean leaves could be used for pest control, but they dry out and don’t last very long. They also can’t easily be applied to locations other than a floor. Synthetic materials could provide a nontoxic alternative.

“Plants exhibit extraordinary abilities to entrap insects,” said Loudon, lead author of the paper. “Modern scientific techniques let us fabricate materials at a microscopic level, with the potential to ‘not let the bedbugs bite’ without pesticides.”

“Nature is a hard act to follow, but the benefits could be enormous,” Potter said. “Imagine if every bedbug inadvertently brought into a dwelling was captured before it had a chance to bite and multiply.”

Here’s a citation and link to the article,

Entrapment of bed bugs by leaf trichomes inspires microfabrication of biomimetic surfaces by Megan W. Szyndler,  Kenneth F. Haynes, Michael F. Potter, Robert M. Corn,
and Catherine Loudon. J. R. Soc. Interface. 2013 10 83 20130174; doi:10.1098/rsif.2013.0174 (published 10 April 2013) 1742-5662

This article is open access.

Moving onto the second bedbug item, Azonano features an Apr. 10, 2013 news item about Fibertrap and its artificial spider web trap for bedbugs,

A breakthrough and innovative solution to the growing plague of bedbugs is about to impact the lives of people suffering from one of the world’s most tenacious pests. Fibertrap is a New York based firm that has developed a revolutionary new way to stop bedbugs, termites and other pests without the use of harmful and toxic chemicals and instead by using an artificial, micro-fiber spider web.

Here’s more about how this solution works,

As the war against bedbugs rages on these nasty insects have become increasingly resistant to pesticides and other common methods of pest control. Fibertrap’s ground-breaking new method addresses the fundamental weakness in all bedbugs and pests: mobility. Utilizing micro-fibers 50 times thinner than human hair, Fibertrap entangles the bugs as they crawl trapping them in the man-made web. Without the ability to move and seek food the creatures will die, ceasing re-production and preventing the establishment of infestation.

Most often, bedbugs move between walls via electrical outlets to unsuspecting home and business owners. To help prevent bedbug migration, Fibertrap intends to produce easy to use traps and insulation products using this innovative new web-like material that will allow the consumer to protect their homes, apartments, offices and dorm rooms with ease and peace of mind.

You can read more about it at Azonano or you can try the Fibertrap website. I cannot find any information about purchasing a Fibertrap product. I think this is publicity designed to excite interest and further investment so these materials ,which are currently at a prototype stage, can be brought to market.

I hope someone is able to get a pest control product for bedbugs to us soon.

Gossamer silk that withstands hurricane force winds

I’ve written about spiderwebs before (mostly recently in my Dec. 9, 2011 posting titled, Music, math, and spiderwebs. Researcher, Markus J. Buehler, was featured in the Dec. 2011 posting and he is featured in this one too. I imagine he’s the ‘go to’ spiderweb researcher at MIT (Massachusetts Institute of Technology).

The most discussed characteristic of spiderwebs is their strength, a topic of endless fascination. The Feb. 1, 2012 news item on physorg.com offers a new take on this phenomenon,

While researchers have long known of the incredible strength of spider silk, the robust nature of the tiny filaments cannot alone explain how webs survive multiple tears and winds that exceed hurricane strength.

Now, a study that combines experimental observations of spider webs with complex computer simulations has shown that web durability depends not only on silk strength, but on how the overall web design compensates for damage and the response of individual strands to continuously varying stresses.

Reporting in the cover story of the Feb. 2, 2012, issue of Nature, researchers from the Massachusetts Institute of Technology (MIT) [team leader Markus Buehler, associate professor of civil and environmental engineering at MIT] and the Politecnico di Torino [team leader Nicola Pugno, Professor of Solid and Structural Mechanics at the Politecnico di Torino] in Italy show how spider web-design localizes strain and damage, preserving the web as a whole.

Very simply, two of the types of spider silk that give the webs their strength were examined separately and together. From the news item,

Viscid silk is stretchy, wet and sticky, and it is the silk that winds out in increasing spirals from the web center. Its primary function is to capture prey. Dragline silk is stiff and dry, and it serves as the threads that radiate out from a web’s center, providing structural support. Dragline silk is crucial to the mechanical behavior of the web.

If you’re a weaver, that description will like remind you of warp and weft. The warp threads provide the strength and remain immobile while the the weft threads are the ones you weave in and out and use to create patterns, etc. if you are so inclined.

These observations about viscid and dragline silk have practical applications (from the news item),

The concept of selective, localized failure for spider webs is interesting since it is a distinct departure from the structural principles that seem to be in play for many biological materials and components,” adds Dennis Carter, the NSF program director for biomechanics and mechanobiology who helped support the study. [emphasis mine]

“For example, the distributed material components in bone spread stress broadly, adding strength. There is no ‘wasted’ material, minimizing the weight of the structure. While all of the bone is being used to resist force, bone everywhere along the structure tends to be damaged prior to failure.”

In contrast, a spider’s web is organized to sacrifice local areas so that failure will not prevent the remaining web from functioning, even if in a diminished capacity, says Carter. “This is a clever strategy when the alternative is having to make an entire, new web!,” he adds. “As Buehler suggests, engineers can learn from nature and adapt the design strategies that are most appropriate for specific applications.”

According to David Kaplan’s Feb. 2, 2012 article for MIT News, the spiderweb’s localized failure was a considered a sign of weakness,

It turns out that a key property of spider silk that helps make webs robust is something previously considered a weakness: the way it can stretch and soften at first when pulled, and then stiffen again as the force of the pulling increases.

This stiffening response is crucial to the way spider silk resists damage. Buehler and his team analyzed how materials with different properties, arranged in the same web pattern, respond to localized stresses. They found that materials with other responses — those that either behave as a simple linear spring as they’re pulled, or start out stretchy and then become more “plastic” — perform much less effectively.

Spider webs, it turns out, can take quite a beating without failing. Damage tends to be localized, affecting just a few threads — the place where a bug got caught in the web and flailed around, for example. This localized damage can simply be repaired, rather than replaced, or even left alone if the web continues to function as before. “Even if it has a lot of defects, the web actually still functions mechanically virtually the same way,” Buehler says. “It’s a very flaw-tolerant system.”

Here’s an image that illustrates how spiderwebs react to stress,

Images show the successive deformation states as loading is increased on a spider web, with red marking high stresses. Simulation picture by S. Cranford & M.J. Buehler/MIT, photographic image by Francesco Tomasinelli & Emanuele Biggi.

The researchers’ article in Nature, Nonlinear material behaviour of spider silk yields robust webs by Steven W. Cranford, Anna Tarakanova, Nicola M. Pugno & Markus J. Buehler is available behind a paywall.

Note: I’m pretty sure I searched to find out if it should be spiderwebs or spider webs. I will investigate further but do not have time now. Meanwhile, I committed to spiderwebs in Dec. 2011.