Researchers have developed a four-dimensional printing technology that allows creation of complex self-folding structures.

The researchers used smart shape memory polymers (SMPs) with the ability to remember one shape and change to another programmed shape when uniform heat is applied.

The technology can have a broad range of applications. For example, an unmanned air vehicle might change shape from one designed for a cruise mission to one designed for a dive.

The technology, developed by researchers at the Georgia Institute of Technology in the US and the Singapore University of Technology and Design (SUTD), could be used to create 3D structures that sequentially fold themselves from components that had been flat or rolled into a tube for shipment.

The components could respond to stimuli such as temperature, moisture or light in a way that is precisely timed to create space structures, deployable medical devices, robots, toys and a range of other structures.

The ability to create objects that change shape in a controlled sequence over time is enabled by printing multiple materials with different dynamic mechanical properties in prescribed patterns throughout the 3D object.

When these components are then heated, each SMP responds at a different rate to change its shape, depending on its own internal clock.

“An important aspect of self-folding is the management of self-collisions, where different portions of the folding structure contact and then block further folding,” the researchers said.

“A metric is developed to predict collisions and is used together with the reduced-order model to design self-folding structures that lock themselves into stable desired configurations,” they noted.