Researchers have created a light-emitting diode (LED) by three-dimensional (3D) printing of five different materials — expanding the number and type of material that can be printed in this way.

This technique involves depositing materials layer by layer until a 3D object is formed. Michael McAlpine and his colleagues at Princeton University in New Jersey used the technology to print a millimetre-sized LED based on quantum dots — nanoscale crystals that emit light.

They seamlessly printed an organic polymer and an indium and gallium metal for the electrodes; a silver metallic interconnect; a layer of quantum dots; and a conductive plastic layer. The entire device was printed onto a curved contact lens.

Other devices, including solar cells and transistors, could be made in this way, the researchers say.

Nano Lett. (2014)