Spider silk shown to conduct heat as effectively as metals

Engineers at Iowa State University have discovered that spider silk conducts heat as well as metals and other highly-conductive material.

The discovery could help create flexible, heat-dissipating parts for electronics and soft materials that release heat during industrial processes.

Spider silk is well-known for its unusual properties. It’s very strong, stretchy and only 4 microns thick, but up until now its thermal conductivity has been a matter of speculation.

Xinwei Wang, an associate professor of mechanical engineering, with support from the Army Research Office and the National Science Foundation, analysed silk from eight different spiders for thermal conductivity.

His research team found that spider silk – particularly the draglines that anchor webs in place – conduct heat better than most materials, including conductors such as silicon, aluminium and pure iron.

Spider silk also conducts heat 1,000 times better than woven silkworm silk and 800 times better than other organic tissues.

“Our discoveries will revolutionise the conventional thought on the low thermal conductivity of biological materials,” said Wang.

He added that spider silk conducts heat at the rate of 416 watts per meter Kelvin, compared with 401 for copper and 0.6 for skin tissues.

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

Even more surprising, he said, is that when spider silk is stretched, its thermal conductivity increases. Wang said stretching spider silk to its 20% limit also increases conductivity by 20%.

The discovery “opens a door for soft materials to be another option for thermal conductivity tuning,” Wang added.

The researchers are now looking at ways of modifying spider silk to enhance its thermal conductivity.