Just as an octopus can change colours and contort its body, so materials built by a 3D printer can alter their hues and morph into new forms.

Qingping Liu at Jilin University in Changchun, China, Lei Ren at the University of Manchester, UK, and their team used 4D printing — the 3D printing of objects that change shape over time — to make soft robots that can remodel themselves.

To do so, the researchers relied on a type of shape-memory polymer, a material that can be ‘programmed’ to change from one shape to another when heated past a certain temperature. The team mixed the polymer with pigments that change colour when heated and return to their original colour when cooled. By controlling factors such as the material’s thickness, the researchers could determine the pace of shape and colour changes.

The authors created a green-and-orange flower bud that opened into a yellow blossom, as well as an octopus with tentacles that changed colour as they unfurled.