Credit: © 2010 AAAS

Viscoelastic materials are both viscous (they can dissipate energy) and elastic (they can reversibly deform and reform). Their uses are widespread and range from biological tissues through everyday objects such as mattresses, to high-performance materials such as vibration isolators. One drawback of many of these materials, however, is the limited temperature range of their optimal performance. Outside these temperatures, they are either brittle or they degrade.

Now, a team from the Japanese National Institute of Advanced Industrial Science and Technology led by Kenji Hata and Don Futaba have created1 a material from carbon nanotubes (CNTs) that is viscoeleastic between −196 °C and 1,000 °C. To create as many physical connections between CNTs as possible, they made randomly oriented, long and clean CNTs, which they then compressed. This quadrupled the density of the material, and scanning electron microscopy revealed a complex structure of interconnected CNTs. The stress–strain behaviour of the compressed material showed that it possessed viscoelastic properties, with stiffness and damping similar to silicone rubber — a known viscoelastic material with the previous best thermal stability.

Comparing the two materials over a large temperature range, however, showed that the silicone rubber degraded at 200 °C, whereas the CNT material's properties did not change at all up to 600 °C. Similarly, the silicone material hardens at −55 °C, but the CNTs maintain their properties down to −140 °C. Repeated stress–strain experiments (even up to one million times) showed that the material has excellent fatigue resistance — Hata, Futaba and colleagues suggest that it dissipates energy through the zipping and unzipping of the tubes at points where two are in contact.