Wires, fibres and elaborate stacks of droplets can be printed in liquid metal.

Most three-dimensional (3D) printing uses molten plastics that cool and harden. This cooling period changes the plastics' mechanical properties, which limits the shapes that can be created. A team led by Michael Dickey at North Carolina State University in Raleigh produced patterns in liquid metal by extruding a gallium–indium alloy through a 3D printer's nozzle at room temperature. On exposure to air, the material instantly formed a roughly nanometre-thick oxide skin, which held the liquid in shape. This layer was sticky and so allowed the team to stack droplets into complex constructions (pictured).

Although the structures were quite weak, the wires made this way could be encased in plastic to form a stretchable, flexible electrical connection between light-emitting diodes.

Adv. Mater. (2013)