Jul 19, 2016 | By Alec

Nanostructures are something of a Holy Grail for material engineers. Consisting of synthesized materials of a nanoscale level, they have numerous mechanical, optical, and energy qualities that could theoretically shake up countless industries. Unfortunately, scaling these materials up to a point where you can work with them has been very challenging. In just about every instance, this diminishes the material’s structural integrity, uniformity and performance – destroying their desirability. But 3D printing might be the solution, as researchers from Virginia Tech have just unveiled a way to successfully scale up nanostructure materials with a 3D printer.

This breakthrough has been realized by a research team led by Xiaoyu Zheng, the assistant professor of mechanical engineering at Virginia Tech. Their findings have been shared in a paper, entitled Multiscale metallic metamaterials, which has just been published in the Nature Materials journal. Also included in the team are Virginia Tech graduate research students Huachen Cui and Da Chen, as well as numerous partners from the Lawrence Livermore National Laboratory (LLNL). The study itself was conducted with support from the LLNL, the SCHEV fund from the state of Virginia, and the Defense Advanced Research Projects agency.

As the researchers explain, they have pioneered a new method for creating metallic nanostructures, which are lightweight, strong and highly elastic. This new 3D printing method can also be significantly scaled up, through a full seven orders of magnitude control– reaching the multiple centimeters in size.

Perhaps the most remarkable characteristic of this new 3D printing breakthrough is the striking level of elasticity it achieves. For these multiscale metallic materials, consisting of hierarchical 3D architectural arrangements and nanoscale hollow tubes, are more than 400 percent more elastic than conventional lightweight metals or ceramic foams. But these multi-leveled hierarchical structures also feature an optimal surface area of nanomaterials, which not only amplifies optical and electrical properties, but also enables photon energy to be collected everywhere – not just on the top surface like a photovoltaic panel, but inside the lattice structure too.

This should pave the way for numerous applications, and should among others enable researchers to mimic a far wider range of natural materials than ever before. Many bone structures, for instance, consist of multiple levels of 3D architectures – from the nanoscale to the macroscale – which researchers have hitherto been unable to fully replicate or control. But any field requiring materials that are stiff, strong, lightweight and very flexible, could also benefit from this breakthrough. Obviously this includes just about any high-tech sector, from the aerospace and automotive to the medical and military industries.

So how does it work? Essentially, they 3D print hierarchical lattices with nanoscale features, producing structures that are mirrored at every scale within the single object. A digital light 3D printing technique is used to overcome the trade-offs between high resolution and build volume, which is often seen as the main obstacle to scaling up 3D printed microlattices and nanolattices. “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,” the researchers write.

But according to Zheng, especially this ability to 3D print these structures on so many orders of magnitude (from the nanoscale to the centimeters) is groundbreaking. “Creating 3D hierarchical micro features across the entire seven orders of magnitude in structural bandwidth in products is unprecedented,” he explained. “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."

This stands in stark contrast to other materials that can be produced at nanoscale, such as graphene sheets. Though 100 times stronger than steel, those graphene properties are almost completely lost when trying to scale up the material in three dimensions – which degrades their strength by up to eight orders of magnitude (making it 100 million times less strong).

While the potential of this new technique is enormous, Zheng and his team are especially thinking about producing multi-functional inorganic materials (such as metals and ceramics) for very harsh environments. “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. Material engineering might never be the same again.



Posted in 3D Printing Application



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Comment wrote at 7/20/2016 10:22:09 AM:

Interesting work. Scalability of two-photon polymerization is still higher even if you take conservative figures like 1cm=10,000,000nm / 500nm = 20,000. Authors claim 16,000 for their method.

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