Graphene octet truss 3D printed by researchers at Virginia Tech College of Engineering and Lawrence Livermore National Laboratory.
Researchers from Virginia Tech and Lawrence Livermore National Laboratory have developed a new way to 3D print with graphene.
The ‘2D material’, known for its superior strength and conductivity, has previously only been used in extrusion-based processes to print single sheets and basic structures at a resolution of around 100 microns. This latest research shows it is now possible to use a stereolithography-based technique to print “pretty much any desired structure” down to 10 microns, close to the size of actual graphene sheets.
Graphene is a single layer of carbon atoms organised in a hexagonal lattice. When graphene sheets are stacked on top of each other in a three-dimensional shape, it becomes graphite, most commonly known as the “lead” in pencils. Graphite itself has poor mechanical qualities but if graphene sheets are separated with air-filled pores, the porous three-dimensional structure, known as a graphene aerogel, can maintain graphene's high performing properties.
“Now a designer can design three-dimensional topology comprised of interconnected graphene sheets,” said Xiaoyu “Rayne” Zheng, assistant professor with the Department of Mechanical Engineering in the College of Engineering and director of the Advanced Manufacturing and Metamaterials Lab. “This new design and manufacturing freedom will lead to optimization of strength, conductivity, mass transport, strength, and weight density that are not achievable in graphene aerogels.”
Close up of a graphene octet-truss scan at a resolution of 10 micrometers.
This project began three years ago, led by Ryan Hensleigh during an internship at the Lawrence Livermore National Laboratory where he worked with Zheng, then a member of the technical staff at the lab.
Hensleigh started with graphene oxide, a precursor to graphene, crosslinking the sheets to form a porous hydrogel. Breaking the graphene oxide hydrogel with ultrasound and adding light-sensitive acrylate polymers, Hensleigh used projection micro-stereolithography to create the desired solid 3D structure with the graphene oxide trapped in the acrylate polymer. Hensleigh then placed the 3D structure in a furnace to burn off the polymers and fuse the object together, leaving behind a pure and lightweight graphene aerogel.
Zheng commented that this technique allowed the team to engineer layers of graphene into any desired freeform shape with a high resolution.
“We’ve been able to show you can make a complex, three-dimensional architecture of graphene while still preserving some of its intrinsic prime properties,” Zheng said. “Usually when you try to 3D print graphene or scale up, you lose most of their lucrative mechanical properties found in its single sheet form.”
The ability to 3D print functional parts in graphene could benefit industries and products including batteries, aerospace, heat management and sensors. The key findings of this work are published in the journal, Materials Horizons.
