Now, 4D printing method to enable shape-changing objects

Scientists have developed a new 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 Boulder incorporated 'shape memory' polymer fibres into the composite materials used in traditional 3D printing, which resulted in the production of shape-changing objects.
The team led by H Jerry Qi, associate professor of mechanical engineering at CU-Boulder, and his collaborator Martin L Dunn of the Singapore University of Technology and Design tested the method for 4D printing.
"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 CU-Boulder mechanical engineering faculty member.

The 4D printing concept, which allows materials to "self-assemble" into 3D structures, was initially proposed by Massachusetts Institute of Technology faculty member Skylar Tibbits in April of 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 CU-Boulder team demonstrated that the orientation and location of the fibres within the composite determines the degree of shape memory effects like folding, curling, stretching or twisting.
The researchers also showed the ability to control those effects by heating or cooling the composite material.
The technology promises exciting new possibilities for a variety of applications.
Qi, who has since joined MIT as a postdoctoral research associate, said that a solar panel or similar product could be produced in a flat configuration onto which functional devices can be easily installed.
It could then be changed to a compact shape for packing and shipping. After arriving at its destination, the product could be activated to form a different shape that optimises its function.

The findings were published in the journal Applied Physics Letters.