Nanostructures made entirely of graphene have been 3-D printed

Korea Electrotechnology Research Institute (KERI) has demonstrated new technique in printing reduced graphene oxide (rGO) nanowires, including straight wires and woven structures.

As reported by, graphene has received a great deal of attention for its promising applications in electronics, biomedical and energy storage devices, and sensors due to properties such as extremely high electron mobility, good thermal conductivity and high elasticity. However, the successful implementation of graphene‐based devices requires the precise patterning of graphene sheets at both the micrometer and nanometer scale. Finding the ideal technique to achieve this remains a major challenge.

3-D printing, also known as additive manufacturing, is becoming a viable alternative to
conventional manufacturing processes in an increasing number of applications ranging
from biomedical science to automobiles to aerospace structures, to name a few. For the first time, researchers have now demonstrated -D printed nanostructures composed entirely of graphene using a new 3-D printing technique. The research team,
led by Professor Seung Kwon Seol from Korea Electrotechnology Research Institute
(KERI), has published their findings in the November 13, 2014 online edition of
Advanced Materials ("3D Printing of Reduced Graphene Oxide Nanowires").

"We developed a nanoscale 3-D printing approach that exploits a size‐controllable
liquid meniscus to fabricate 3-D reduced graphene oxide (rGO) nanowires," Seol
explained. "Different from typical 3-D printing approaches which use
filaments or powders as printing materials, our method uses the stretched liquid
meniscus of ink. This enables us to realize finer printed structures than a nozzle
aperture, resulting in the manufacturing of nanostructures."

The researchers noted that their novel solution‐based approach is quite effective in 3-D
printing of graphene nanostructures as well as in multiple‐materials 3-D nanoprinting.
"We are convinced that this approach will present a new paradigm for implementing
3-D patterns in printed electronics," says Seol.

For their technique, the team grew graphene oxide (GO) wires at room temperature
using the meniscus formed at the tip of a micropipette filled with a colloidal dispersion
of GO sheets, then reduced it by thermal or chemical treatment (with hydrazine).

The deposition of GO was obtained by pulling the micropipette as the solvent rapidly
evaporated, thus enabling the growth of GO wires. The researchers were able to
accurately control the radius of the rGO wires by tuning the pulling rate of the pipeline;
they managed to reach a minimum value of ca. 150 nm.

Using this technique, they were able to produce arrays of different freestanding rGO
architectures, grown directly at chosen sites and in different directions: straight wires,
bridges, suspended junctions, and woven structures.

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