This object is printed flat (left) and can later be altered in two stable and load-bearing forms (middle and right). (Credit: ETH Zurich/Tian Chen)

Scientists use the term 4D printing to refer to the simple production of objects that can transform their shape at different times. Researchers have now taken this approach a major step further by developing a construction principle that can produce load-bearing and predictable structures.

The new principle allows the researchers to control the deformation. The structures can also support weight. The structural principle depends on an actuating element developed by the scientists to take on two possible states: retracted or extended. The researchers combined these elements to create more complex structures. One possible application for 4D printing is the creation of stents.

The individual elements can assume only one of the two specific states, so the researchers can predict the stable three-dimensional form of the overall structure. This also allows structures that can take on several stable forms. They have also developed simulation software so that they can predict accurately the shapes and the force that must be applied to produce the deformation.