Ever since single-layer graphene burst onto the science scene in 2004, the possibilities for the promising material have seemed nearly endless. With its high electrical conductivity, ability to store energy, and ultra-strong and lightweight structure, graphene has potential for many applications in electronics, energy, the environment, and even medicine.
Now a team of Northwestern University researchers has found a way to print three-dimensional structures with graphene nanoflakes. The fast and efficient method could open up new opportunities for using graphene printed scaffolds regenerative engineering and other electronic or medical applications.
Led by Ramille Shah, assistant professor of materials science and engineering at the McCormick School of Engineering and of surgery in the Feinberg School of Medicine, and her postdoctoral fellow Adam Jakus, the team developed a novel graphene-based ink that can be used to print large, robust 3-D structures.
With a volume so meager, those inks are unable to maintain many of graphene’s celebrated properties. But adding higher volumes of graphene flakes to the mix in these ink systems typically results in printed structures too brittle and fragile to manipulate. Shah’s ink is the best of both worlds. At 60-70 percent graphene, it preserves the material’s unique properties, including its electrical conductivity. And it’s flexible and robust enough to print robust macroscopic structures. The ink’s secret lies in its formulation: the graphene flakes are mixed with a biocompatible elastomer and quickly evaporating solvents
“It’s a liquid ink,” Shah explained. “After the ink is extruded, one of the solvents in the system evaporates right away, causing the structure to solidify nearly instantly. The presence of the other solvents and the interaction with the specific polymer binder chosen also has a significant contribution to its resulting flexibility and properties. Because it holds its shape, we are able to build larger, well-defined objects.”
An expert in biomaterials, Shah said 3-D printed graphene scaffolds could play a role in tissue engineering and regenerative medicine as well as in electronic devices. Her team populated one of the scaffolds with stem cells to surprising results. Not only did the cells survive, they divided, proliferated, and morphed into neuron-like cells.