The team led by H Jerry Qi, associate professor of mechanical engineering at University of Colorado, and his collaborator Martin L Dunn of the Singapore University of Technology and Design tested the method for 4D printing which enables production of objects fixed in one shape that can later be changed to take on a new shape.

Researchers from the University of Colorado incorporated shape memory polymer fibres into the composite materials used in traditional 3D printing, which resulted in the production of shape-changing objects.

"In this work, the initial configuration is created by 3D printing, and then the programmed action of the shape memory fibres creates time dependence of the configuration, the 4D aspect," said Dunn, a former University of Colorado, mechanical engineering faculty member.

The 4D printing concept was initially proposed by Massachusetts Institute of Technology faculty member Skylar Tibbits in April this year. Tibbits and his team combined a strand of plastic with a layer made out of smart material that could self-assemble in water.

"We advanced this concept by creating composite materials that can morph into several different, complicated shapes based on a different physical mechanism," said Dunn.

"The secret of using shape memory polymer fibres to generate desired shape changes of the composite material is how the architecture of the fibres is designed, including their location, orientation and other factors," Dunn added.

The technology promises exciting new possibilities for a variety of applications. The US army research office is hoping 4D printing will lead to materials that allow cars to change their structure or a fabric that enables a soldier’s uniform to alter its camouflage.