Graphene structures created with 3D printing

Super-strong, super-light, durable-yet-flexible two-dimensional material graphene is often hailed as the wonder material of the future. Able to conduct both heat and electricity with great efficiency, its potential for use in electronics manufacturing is enormous -- OLEDs, batteries, transistors and photovoltaic cells are just a few in a long list of ways in which the material may be used.

As you can probably imagine, combining this with 3D printing is sort of a manufacturing holy grail. Last year, it was achieved for the first time by a team of researchers in Korea, who managed to 3D print graphene nanowires.

Now a team of researchers from the Imperial College London, the University of Warwick, has created a graphene 3D printing material that they have printed into more complex three-dimensional geometric arrangements.

"Our formulations have the flow and physical properties we need for the filament deposition process required in 3D printing: They need to flow through very small nozzles and set immediately after passing through it, retaining the shape and holding the layers on top," lead author Dr Esther García-Tuñon of Imperial College London explained to Nanowerk.

"We use this two-dimensional material as building block to create macroscopic 3D structures and a technique called direct ink writing also known as direct write assembly, or Robocasting."

The original goal was to print graphene structures -- not composites -- using very small amounts of additive for a water-based ink. The problem with that is graphene is highly hydrophobic, so a water-based ink is impossible to formulate. For this reason, the team developed its ink out of graphene oxide -- a chemically modified form of graphene that can be processed in water.

The graphene "ink" the team came up with combines flakes of graphene oxide and reduced graphene oxide with small amounts of responsive polymer -- that is, a "smart" polymer that can change its shape and behaviour in response to a certain trigger, such as temperature or a certain chemical. This ink acts like 3D printing filament, allowing the team to 3D print nanostructures.

"Our inks allow printing through nozzles as thin as 100 µm [1/10 of a millimietre] and their rheology could also be tailored for other processing technologies such as extrusion, gel, or tape casting," Dr García-Tuñon said.

She was careful, however, to note that this is only a very early step.

"The buzzword 3D printing is now everywhere; we can find many examples of commercially available 3D printers to make your own Hello Kitty, iPhone cases, and all sort of plastic models," she said. "But there is still a long way to go from here to the use of 3D printing for a wide variety of materials in multicomponent and practical devices."

The researchers are currently working with Imperial Innovations to find ways to commercialise the technology; applications being explored include pressure-sensitive skin for robotics and membranes for cleaning oil spills. The full study, which was published in the journal Advanced Materials, can be found online.