4D Printing: When 3D changes its shape over time

It was clear that even the 3D printing would someday be an “old hat”. A process developed by researchers at ETH Zurich now allows 4D printing – “printing in four dimensions”.

The point is that the 3D-printed objects can change in time depending on their shape. For example, they fold from a flat kit to a curved construct. Thus, it is possible to produce predictable and load-bearing structures. The scientists around Kristina Shea from the ETH Zurich have developed this design principle, which allows precise control of the shape changes during 4D printing.

The researchers developed a special lifting element, which can only switch between two states: retracted or extended. It consists of a rigid polymer for the immovable components, and an elastic for the mobile. These components were produced by Chen and his colleagues in one step in a multi-material 3D printer.

A single lifting element in its two states. It consists of a rigid (light) and elastic (dark) polymer. (Figure: Chen et al., Scientific Reports, 2017)
Because the individual elements can only occupy one of two states, the more complex structures composed therefrom are also predictable.

The structures still have to be developed manually. In the next step, the scientists are working on appropriate drives. These structures are expected to be temperature-dependent. Also possible would be a control with compressed air or swelling material, which changes by moisture form.

Flat structures can be transported in a space-saving manner and unfold only at the destination.
The application area would be, for example, space travel, which has already pursued similar approaches for some time, building technology or medicine. For example, a new generation of stents, supporting scaffolds, would support the body vessels and keep them open. With 4D pressure they could unfold only after the insertion into the body.