Cross-sectional scanning electron microscopy image of the 3DGraphene foam with a homogeneous and highly porous structure.

Graphene foam keeps its elasticity when all other materials are frozen stiff. Credit: K. Zhao et al./Sci. Adv.

Materials science

The solid that remains flexible at temperatures close to absolute zero

A spongy form of graphene can also maintain its resilience when subjected to extreme heat.

The wonder-material graphene has gained yet another superlative: exceptional flexibility at temperatures at which everything else is frozen solid.

Graphene consists of a single layer of carbon atoms, and is the thinnest and strongest material known, the best at conducting both heat and electric current, and almost totally transparent to wavelengths of light ranging from the ultraviolet to the infrared. Pulickel Ajayan at Rice University in Houston, Texas, Yongsheng Chen at Nankai University in Tianjin, China, and their colleagues made graphene foam and deformed it repeatedly. The foam’s elasticity remained essentially unchanged at temperatures ranging from -269°C (4 kelvin) to 1000°C. Silicone rubber, by contrast, becomes hard and brittle at -55°C and melts at 300°C.

The researchers also found that the foam can stretch to almost twice its length and return to its original shape even when chilled to -269°C, the temperature at which helium liquefies. Every other known material becomes completely inflexible when chilled to a few tens of degrees below 0°C. Graphene’s elasticity over a wide temperature range could make it useful in extreme environments such as outer space.