Spider silk is superb conductor of heat

Posted by Emma Woollacott

Spider silk conduct heat as well as metals do, an Iowa State University professor has discovered.

Indeed, spider silk - especially the draglines that anchor webs in place - is a better thermal conductor than silicon, aluminum and pure iron, and 800 times better than other organic tissues.

It conducts heat at the rate of 416 watts per meter Kelvin, compared with 401 for copper and 0.6 for skin tissues.

"Our discoveries will revolutionize the conventional thought on the low thermal conductivity of biological materials," says Xinwei Wang.

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

Even more surprising, he says, is that when spider silk is stretched, its thermal conductivity goes up. While most materials lose thermal conductivity when stretched, stretching spider silk to its 20 percent limit also increases conductivity by 20 percent.

The reason for spider silk's unusual heat-carrying properties, says Wang, is its  defect-free molecular structure, including proteins that contain nanocrystals and the spring-shaped structures connecting the proteins.

The discovery means soft materials could be another option for thermal conductivity tuning, says Wang.

Spider silk could be used to help create flexible, heat-dissipating parts for electronics, better clothes for hot weather, bandages that don't trap heat and many other everyday applications.