Michael McAlpine and his McAlpine Group at Princeton have focused on nanotechnology materials with their distinct mechanical properties to create fundamental and applied investigations in the biomedical and energy sciences, and their 3D printed projects boast unique geometries, properties and functionality.

In the past, the McAlpine team has created power-generating rubber films meant to capture natural body movements like breathing and walking to power electronic devices. Those ceramic nanoribbons were embedded onto silicone rubber sheets to generate electricity when flexed, and now the team has made materials which can be 3D printed to create LED lighting.

Michael McAlpine

Made from five different materials; emissive semiconducting inorganic nanoparticles, an elastomeric matrix, organic polymers used as charge transport layers, solid and liquid metal leads and a UV-adhesive transparent substrate layer, the researchers say the new method is a proof of concept aimed at demonstrating the possibility of making quantum dot light-emitting diodes capable of "pure and tunable color emission properties."

They say the printed LEDs might, given the ability to print onto curvilinear surfaces, one day revolutionize the production of everything from electronic devices to contact lenses to biomedical implants.

At this point, the researchers have used microfabrication techniques to construct a cube of encapsulated LEDs and every component of the cube and electronics were 3D printed using many distinct classes of materials.

Working with Yong Lin Kong, Ian Tamargo, Hyoungsoo Kim, Blake Johnson, Maneesh Gupta, Tae-Wook Koh, Huai-An Chin, Daniel A Steingart and Barry P. Rand, McAlpine and his team made the LEDs using a custom 3D printer which took them six months and nearly $20,000 to assemble.

Comprised of five layers, the printed LEDs include a metal ring of silver nanoparticles, two polymer layers which supply and shuttle electrical current to a third layer of "quantum dots" composed of cadmium selenide nanoparticles within a zinc sulfide shell and a cathode ray layer made of eutectic gallium indium.

It all adds up to a device which forces electrons to slam into the quantum dots and emit orange or green light.

McAlpine believes that 3D printing, with its ability to deliver a third dimension, will be used to manufacture "things that people haven't imagined yet, like structures that could be used in the body."

McAlpine's Princeton team, the first to combine silicone and nanoribbons of lead zirconate titanate – or PZT – also fabricated nanoribbons from the material so thin that some 100 of them can fit side-by-side within the space of a single millimeter.