Virginia Tech Researchers Use 3D Printing to Scale Nanotechnology Up & Harness Special Mechanical Properties

You would be hard pressed today to find a technology more versatile than 3D printing. Making significant impacts that span nearly every industry worldwide, whether you are considering dental 3D printers, titanium spinal implants, luxury car components, or futuristic buildings, we’re witnessing many changes we just never expected. But 3D printing also offers versatility in materials, from metal to PEEK—as well as shapes and sizes and properties. There is a machine for every job it would seem, from the macro- to the micro-level. And while we certainly see innovations emerging from the tiny to the enormous, there is a great deal of interest in 3D printing at the super tiny level—as in nano.

Smaller than tiny and tinier than micro, the nanoscale operates at one billionth of a meter or better yet, as 25,400,000 nanometers in an inch. And this is where the hearts of many researchers lie as they work diligently, innovating in the realm of materials science and 3D printing. At Virginia Tech, however, researchers are not content with operating with nanos. They want to see if they can scale them right back up as well and still retain the use of their special qualities. Just for fun? Well, if you’ve got skills like that in the science lab, undoubtedly there’s some fun involved, but Xiaoyu “Rayne” Zheng is more interested in the ability to control these properties for architectures used in many different important applications from space technology to the automotive industry.

Xiaoyu “Rayne” Zheng

Zheng has outlined his current findings in ‘Multiscale Metallic Metamaterials,’ just published in Nature Materials and co-authored by William Smith, Julie Jackson, Bryan Moran, Huachen Cui, Da Chen, Jianchao Ye, Nicholas Fang, Nicholas Rodriguez, Todd Weisgraber, and Christopher M. Spadaccini. Here, they discuss the issues caused by scalability limitations, and their plans to overcome that within the realm of nanoarchitectures, demonstrating the levels of metamaterials with different 3D features, over seven orders of magnitude, ranging from the nanometer to the centimeter.

Working at the macroscale, metamaterials were able to reach a high tensile elasticity greater than 20 percent. The research team points out that this was at a constant strength, and a flexibility not found in their ‘brittle-like’ metallic counterparts.

“Creation of these materials is enabled by a high-resolution, large-area additive manufacturing technique with scalability not achievable by two-photon polymerization or traditional stereolithography,” said the research team in their paper. “With overall part sizes approaching tens of centimeters, these unique nanostructured metamaterials might find use in a broad array of applications.”

With their new process, the researchers were able to go from the nano-level to larger sizes for optimizing a variety of valuable properties such as mechanical, optical, and energy. These properties have previously only been accessible at the nano-level, but with the elasticity in these metallic materials, along with their 3D architectural arrangement and nanoscale hollow tubes, an increase of 400% in tensile elasticity can be achieved. Employing multiple levels of 3D lattices that still offer the features found at the nanoscale, researchers are optimistic that indeed the material will be helpful in many important applications to include batteries, flexible armors, and small, lightweight cars.

Zheng and his team use a digital light 3D printing technique that allows them to scale the materials without worrying about sacrificing resolution or build size.

“Creating 3-D hierarchical micro features across the entire seven orders of magnitude in structural bandwidth in products is unprecedented,” said Zheng, the lead author of the study and the research team leader. “Assembling nanoscale features into billets of materials through multi-leveled 3-D architectures, you begin to see a variety of programmed mechanical properties, such as minimal weight, maximum strength, and super elasticity at centimeter scales.”

Generally the problem with attempting to scale nanomaterials, like graphene, is that as they are made larger, they become exponentially weaker.

“The increased elasticity and flexibility obtained through the new process and design come without incorporating soft polymers, thereby making the metallic materials suitable as flexible sensors and electronics in harsh environments, where chemical and temperature resistance are required,” Zheng said.

The study shows that in using the hierarchical lattice with multiple levels, there’s more opportunity to collect and use photon energy from the surface area, as it is available more freely, and not just limited to the surface. The potential is great here, and as researchers explore further, we should find out more about the production of ‘multi-functional inorganic materials,’ as well as metals and ceramics.

Additional team members include Virginia Tech graduate research students Huachen Cui and Da Chen from Zheng’s group, and colleagues from Lawrence Livermore National Laboratory. The research was conducted under Department of Energy Lawrence Livermore Laboratory-directed research support with additional support from Virginia Tech, the SCHEV Fund from the commonwealth of Virginia, and the Defense Advanced Research Projects Agency. Discuss further in the 3D Printing & Scaling Nanomaterials forum over at 3DPB.com.