For the first time in history, a team from the Korea Electrotechnology Research Institute (KERI), has managed to demonstrate 3D printed nanostructures made entirely of graphene, the unique and promising 'material of the future.'
The revolutionary approach, which was published in the November 33, 2014 edition of Advanced Materials, involves using the stretched liquid meniscus of ink to fabricate 3D reduced graphene oxide (rGO) nanowires. Unlike most 3D printing methods, which use filaments or powders as printing materials, KERI's method is more refined. "This enables us to realize finer printed structures than a nozzle aperture, resulting in the manufacturing of nanostructures," said research team leader, Professor Seung Kwon Seol.
This is an important advancement for the implementation of 3D patterns in printed electronics, in which the use of graphene plays a very important role.
Formed by a single layer of carbon atoms only one atom thick and in the shape of a hexagonal lattice, graphene is the fundamental building block of all graphitic materials. It is known for its unique properties, such as extraordinary conductivity, flexibility and transparency, making it an ideal material for everything from electronics to energy storage to commercial applications. However, the challenge for scientists is to manipulate graphene sheets at both the micrometer and nanometer scale, which requires a high degree of precision. The additive manufacturing process of 3D printing just may be the solution.
As described in their article, Professor Seol's team used liquid meniscus as a more novel approach to nanometer-scale 3D printing. Graphene oxide (GO) wires were grown at room temperature using the meniscus formed at the tip of a micropipette. The wires were then reduced by thermal or chemical treatment (with hydrazine). GO deposition was achieved by pulling the micropipette as the solvent rapidly evaporated, thus enabling the growth of GO wires.
Schematic diagram of GO nanowire fabrication by pulling a micropipette filled with an aqueous GO suspension (GO sheet thickness = 0.9 ± 0.1 nm) and stretching the meniscus during water evaporation. In the circle (lower right): FE-SEM image showing a grown rGO nanowire with r = 400 nm. viaNanowerk & Advanced Materials
By tuning the pulling rate of the pipette, the researchers could accurately control the rGO wires and were able to reach a minimum value of ca. 150nm. The researchers note that their approach is quite effective in 3D printing of graphene nanostructures as well as in multiple-materials 3D nanoprinting. With this technique, they produced a variety of freestanding rGO architectures, including straight wires, bridges, suspended junctions and woven structures.

To date, composite filaments for the 3D printing of graphene-enhanced plastic structures using an FDM printer has already been proposed, but it does pose some difficulties. While the graphene used in this composite scenario improves the properties of the plastic, the plastic materials simultaneously deteriorate the intrinsic properties of the graphene. Furthermore, the conventional FDM printing method cannot accurately downsize printed structures to the required nanometer scale.
"To the best of our knowledge, nobody has reported 3D-printed nanostructures composed entirely of graphene," said Professor Seol.
"We are convinced that this approach will present a new paradigm for implementing 3D patterns in printed electronics," he continued. Indeed this fascinating advancement in 3D nanoprinting technology is effective in the 3D printing of graphene nanostructures as well as in multi-material nanoprinting, and it can be implemented into various electronic industries, such as 3D printed circuit bards, transistors, solar cells, and sensors, to name a few.
While some challenges still remain, such as reducing the 3D printable size from 150 nm to below 10 nm, the use of graphene in 3D printing technologies is looking more promising than ever.
By 3ders