Self-healing 'smart' material changes shape with heat, light

Scientists have developed a new smart material that can heal itself and change shape when exposed to heat and light, which may be used in drug delivery systems and self-assembling devices.
This is the first time researchers have been able to combine several smart abilities, including shape memory behaviour, light-activated movement and self-healing behaviour, into one material.
Smart materials that can react to external stimuli, like light or heat, have been an interesting novelty and look almost magical as they mysteriously fold and unfold themselves, according to researchers from Washington State University and Oak Ridge National Laboratory in the US.

They have a variety of potential applications, such as for actuators, drug delivery systems and self-assembling devices.
For instance, smart materials could change shape to unfold a solar panel on a space satellite without the need of a battery-powered mechanical device.
However, smart materials have not come into widespread use because they are difficult to make and often can only perform one function at a time.

Researchers also have struggled to reprocess the material so its special properties can continually repeat themselves.
The researchers developed a material that allows multiple functions at once with potential to add more.
The team worked with a class of long-chain molecules, called liquid crystalline networks (LCNs), which provide order in one direction and give material unique properties.

The researchers took advantage of the way the material changes in response to heat to induce a unique three-way shape shifting behaviour.
They added groups of atoms that react to polarised light and used dynamic chemical bonds to improve the material's reprocessing abilities.
"We knew these different technologies worked independently and tried to combine them in a way that would be compatible," said Michael Kessler, from WSU School of Mechanical and Materials Engineering (MME), who led the study.
The resulting material reacts to light, can remember its shape as it folds and unfolds and can heal itself when damaged.
For instance, a razor blade scratch in the material can be fixed by applying ultraviolet light. The material's movements can be preprogrammed and its properties tailored.

The study was published in the journal ACS Applied Materials and Interfaces.