Over the years, we've seen Spiderman use his webbing to catch villains, swing between buildings, and even parachute from great heights. In all that time, however, the opportunity never came up for him to use it to conduct heat. As it turns out, it would have been perfect for the job. Although materials from living things generally don't conduct heat well, a team of scientists from Iowa State University have discovered that spider silk does so 800 times better than any other organic material ever tested. Because the silk is also very strong and stretchable, it could have a number of applications in human technology.
Associate professor of mechanical engineering Xinwei Wang started with eight captive golden silk orbweaver spiders, and gathered the silk that they spun in their cages. When his research team tested the thermal conductivity of the fiber, they discovered that it conducted heat better than any other organic material, and better than most materials commonly used for the task - materials including silicon, aluminum and pure iron. In fact, he claimed that only silver and diamond perform better.
Specifically, the silk was shown to conduct heat at a rate of 416 watts per meter Kelvin. By contrast, copper comes in at 401, while skin tissue only manages a 0.6. Even when compared to woven silkworm silk, which many people might expect to perform similarly, the spider silk was still 1,000 times better. The draglines that the spiders use to anchor their webs in place showed the best conductivity of all.
The amazing qualities don't stop there, however. When the silk was stretched to its 20 percent limit, its conductivity correspondingly went up by 20 percent. This runs contrary to the characteristics of most materials, which lose thermal conductivity as they're stretched.
Although he believes that more research still needs to be conducted, Wang has stated that spider silk's conductivity is due at least partly to its defect-free molecular structure. That structure incorporates proteins that contain nanocrystals, and that are connected to one another by spring-shaped structures. He is now looking into modifying the structure of the silk, to boost its thermal conductivity even higher.
Down the road, he thinks that the material could be used in applications such as flexible heat-dissipating materials for electronics, bandages that stay cool, and clothes for hot climates.
Other recent studies have shown that spider silk holds promise for use in things such as gene therapy, bioadhesives, pesticides, and microneedles.
A paper on Wang's research was recently published in the journal Advanced Materials.
Source: Iowa State University
