Heat-activated self-stretching material ‘offers engineering benefits’

A new study has demonstrated the potential engineering benefits offered by a new class of rubber-like material that is able to change shape in response to temperature.

As described in the scientific journal ACS Macro Letters, the material works like a shape-memory polymer that can be switched between two different shapes. However, it does not need to be programmed with each cycle – instead, it can repeatedly switch shapes with no external forces, simply upon cooling and heating.

The material incorporates polymer strands that are loosely connected by bonds called crosslinks to create a network of molecules. It was then stretched into the desired shape, before more crosslinks were added and the polymer was cooled causing crystallisation to occur in a certain direction.

These internal crystallisation forces then force the material to assume the same shape upon cooling, before reverting back to its original form when heated. Moreover, there was no limit to the number of times this process could repeat itself.

Mitchell Anthamatten, an associate professor of chemical engineering at the University of Rochester, said: "The next step is to optimise the shape of the polymer material and the energy released during the process. That will be done by adjusting the type and density of crosslinks that tie the individual chains together."

This innovation could potentially be applied to several areas where reversible shape-changes may be needed during operations, including biotechnology, artificial muscles and robotics.