Study suggests origin of elasticity could lie in how molecules interact under stress

A study has suggested that elasticity in an object possibly originates in the interactions between molecules of the flexible material, allowing it to regain its original shape once the external stress is removed. The findings open the door for the design of new and elastically flexible crystals which could be used in spacecraft or electronic devices, the authors wrote in the study published in the journal Nature Materials.

The researchers, including from The University of Queensland, Australia, had set out to try and locate the exact "location" of the force stored in an flexible material which gives it elasticity.

To understand this, the team bent single crystals of three molecular materials -- which retain their properties at a molecule's level -- to locate precisely where the energy is stored.


"We looked at how and where the energy was stored as the crystals contracted and went back to their original shape and size," author Jack Clegg, a professor at the school of chemistry and molecular biosciences, The University of Queensland, said.

The researchers found that the energy that allowed the crystals to spontaneously straighten out and spring back to its original shape was stored as potential energy in the interactions between the molecules.

"We were able to show that enough energy was stored in our bent flexible crystals to lift something 30 times the weight of the crystal a metre into the air," Clegg said.

The author added, "Under strain, the molecules reversibly rotate and reorganise in a way that stores energy differently on the inside and the outside of the bend."

The new understanding of this commonly observed phenomenon could allow the design of new hybrid materials that could find their use in spacecrafts or electronic devices, Clegg said.

"Elasticity is a property that underpins a myriad of existing technologies including optical-fibres, aeroplane components and load-bearing bridges," the author said.

"We show for each material that different intermolecular interactions are responsible for the restoring force under both expansive (tension) and compressive strain," the authors wrote.