Spider silk conducts heat as well as metals, study finds

Mar 05, 2012
This is one of the golden silk orbweavers spinning webs for Xinwei Wang's research project. Credit: Photo courtesy of the Xinwei Wang research group

Xinwei Wang had a hunch that spider webs were worth a much closer look.

So he ordered eight – Nephila clavipes, golden silk orbweavers – and put them to work eating crickets and spinning webs in the cages he set up in an Iowa State University greenhouse.

Wang, an associate professor of mechanical engineering at Iowa State, studies , the ability of materials to conduct . He's been looking for organic materials that can effectively transfer heat. It's something diamonds, copper and aluminum are very good at; most materials from living things aren't very good at all.

But has some interesting properties: it's very strong, very stretchy, only 4 microns thick (human hair is about 60 microns) and, according to some speculation, could be a good conductor of heat. But nobody had actually tested spider silk for its thermal conductivity.

And so Wang, with partial support from the Army Research Office and the National Science Foundation, decided to try some lab experiments. Xiaopeng Huang, a post-doctoral research associate in mechanical engineering; and Guoqing Liu, a doctoral student in mechanical engineering, helped with the project.

"I think we tried the right material," Wang said of the results.

Xinwei Wang, Guoqing Liu and Xiaopeng Huang, left to right, show the instruments they used to study the thermal conductivity of spider silk. Credit: Photo by Bob Elbert/Iowa State University

What Wang and his research team found was that spider silks – particularly the draglines that anchor webs in place – conduct heat better than most materials, including very good conductors such as silicon, aluminum and pure iron. Spider silk also conducts heat 1,000 times better than woven silkworm silk and 800 times better than other organic tissues.

A paper about the discovery – "New Secrets of Spider Silk: Exceptionally High Thermal Conductivity and its Abnormal Change under Stretching" – has just been published online by the journal Advanced Materials.

"Our discoveries will revolutionize the conventional thought on the low thermal conductivity of biological materials," Wang wrote in the paper.

The paper reports that using laboratory techniques developed by Wang – "this takes time and patience" – spider silk conducts heat at the rate of 416 watts per meter Kelvin. Copper measures 401. And skin tissues measure .6.

"This is very surprising because spider silk is organic material," Wang said. "For organic material, this is the highest ever. There are only a few materials higher – silver and diamond."

Even more surprising, he said, is when spider silk is stretched, thermal conductivity also goes up. Wang said stretching spider silk to its 20 percent limit also increases conductivity by 20 percent. Most materials lose thermal conductivity when they're stretched.

That discovery "opens a door for soft to be another option for thermal conductivity tuning," Wang wrote in the paper.

And that could lead to spider silk helping to create flexible, heat-dissipating parts for electronics, better clothes for hot weather, bandages that don't trap heat and many other everyday applications.

What is it about spider silk that gives it these unusual heat-carrying properties?

Wang said it's all about the defect-free molecular structure of spider silk, including proteins that contain nanocrystals and the spring-shaped structures connecting the proteins. He said more research needs to be done to fully understand spider silk's heat-conducting abilities.

Wang is also wondering if spider silk can be modified in ways that enhance its thermal conductivity. He said the researchers' preliminary results are very promising.

And then Wang marveled at what he's learning about spider webs, everything from spider care to web unraveling techniques to the different silks within a single web. All that has one colleague calling him Iowa State's Spiderman.

"I've been doing thermal transport for many years," Wang said. "This is the most exciting thing, what I'm doing right now."

Explore further: Aromatic couple makes new chemical bonds

Related Stories

Most stretchable spider silk reported

Feb 08, 2012

The egg sac silk of the cocoon stalk of the cave spider Meta menardi is the most stretchable egg sac silk yet tested, according to a study published Feb. 8 in the open access journal PLoS ONE.

Silkworms spinning spider webs

Jan 03, 2012

(PhysOrg.com) -- A spiders silk is strong and more elastic and has a large range of possible medical applications. However, spiders have a history of being territorial and prone to cannibalism, so the idea ...

Stretchy spider silks can be springs or rubber

May 31, 2008

It’s stronger than steel and nylon, and more extensible than Kevlar. So what is this super-tough material? Spider silk; and learning how to spin it is one of the materials industries’ Holy Grails. John Gosline has been ...

Recommended for you

New CMI process recycles magnets from factory floor

2 hours ago

A new recycling method developed by scientists at the Critical Materials Institute, a U.S. Department of Energy Innovation Hub led by the Ames Laboratory, recovers valuable rare-earth magnetic material from ...

Chemists characterize 3-D macroporous hydrogels

6 hours ago

Carnegie Mellon University chemists have developed two novel methods to characterize 3-dimensional macroporous hydrogels—materials that hold great promise for developing "smart" responsive materials that ...

Substrates change nanoparticle reactivity

12 hours ago

(Phys.org)—Nanoscale materials tend to behave differently than their bulk counterparts. While there are many theories as to why this happens, technological advances in scanning tunneling microscopy (STM) ...

Reviving cottonseed meals adhesives potential

14 hours ago

Cottonseed meal—the leftovers after lint and oil are extracted from cottonseed—is typically fed to ruminant livestock, such as cows, or used as fertilizer. But Agricultural Research Service scientists ...

New concrete composite can heal itself

14 hours ago

In the human body, small wounds are easily treated by the body itself, requiring no further care. For bigger wounds to be healed, the body may need outside assistance. Concrete is like a living body, in that ...

Actuators that mimic ice plants

15 hours ago

Engineers developing moveable robot components may soon take advantage of a trick plants use. Researchers at the Max Planck Institute of Colloids and Interfaces in Potsdam and Harvard University in Cambridge ...

User comments : 10

Adjust slider to filter visible comments by rank

Display comments: newest first

4 / 5 (2) Mar 05, 2012
Spider silk conducts heat at the rate of 416 watts per meter Kelvin. Copper measures 401

That's an amazing result. This research could have profound impact on materials science if they figure out how to engineer this deliberately. This is a "Big Deal" experiment.
5 / 5 (1) Mar 05, 2012
I'm wondering what advantage thermally conductive spider silk might be to the spider? I could see how vibration conductivity, maybe electrical conductivity, would benefit a spider. This makes the web a big sensor for the spider, extending her senses beyond her own body.
1.6 / 5 (5) Mar 05, 2012
Am I the only one thinking about the possibility of lighter spacesuits and Firefighting gear? Build the layer that touches the skin with this material and then control that layer directly to maintain optimum temperature.
5 / 5 (3) Mar 05, 2012
As an emeritus fireman, I am wondering why conductivity would be beneficial given that high insulation, moisture control through vapor barriers, and reflectivity at times is what is sought after. It seems that any added material added would be most useful if it simply added insulation against high heat. If it could be used somehow to aide internally cooling, then that would be useful. I would think the same would be true in space suits.
1 / 5 (2) Mar 05, 2012
It's a bit suspicious result for me: people made large pieces of clothes from spider silk - how is it possible, nobody recognized it already?

1 / 5 (1) Mar 05, 2012
i didnt know silver was organic. organic means carbon, right? but isnt silver just silver? an element of its own?
5 / 5 (2) Mar 05, 2012
Combine these abilities with a company (Kraig Biocraft Laboratories, Inc. (KBLB)) that is on the verge of getting genetically modified silk-worms to spin spider silk, and you might see a lot more spider silk in a LOT of products here in the near future.
5 / 5 (1) Mar 06, 2012
Tiburon, I am not sure just getting silk worms to produce spider silk will be enough, there are probably a lot of subtle details in the production process that you don't automatically copy by moving a bloc of DNA from one species to another...but it would be terrific if it works on the first try.
1.4 / 5 (9) Mar 06, 2012
Kraig Biocraft Laboratories, Inc. (KBLB)) that is on the verge of getting genetically modified silk-worms to spin spider silk

Wait, what? I thought they'd already achieved this.

Cluebat from Exodar
not rated yet Mar 06, 2012

Goats can produce this protein. Now we just need to develope machines to fabricate the monofilaments.

Or maybe Darpa is on that now.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.