For years, scientists and engineers
have synthesized materials at the nanoscale level to take advantage of their mechanical,
optical, and energy properties, but efforts to scale these materials to larger
sizes have resulted in diminished performance and structural integrity.
Now, researchers led by Xiaoyu
"Rayne" Zheng, an assistant professor of mechanical engineering at
Virginia Tech have published a study in the journal Nature Materials
that describes a new process to create lightweight, strong and super elastic
3-D printed metallic nanostructured materials with unprecedented scalability, a full
seven orders of magnitude control of arbitrary 3-D architectures.
Strikingly, these multiscale metallic
materials have displayed super elasticity because of their designed
hierarchical 3-D architectural arrangement and nanoscale hollow tubes,
resulting in more than a 400 percent increase of tensile elasticity over
conventional lightweight metals and ceramic foams.
The approach, which produces multiple
levels of 3-D hierarchical lattices with nanoscale features, could be useful anywhere
there's a need for a combination of stiffness, strength, low-weight, high
flexibility—such as in structures to be deployed in space, flexible armors,
lightweight vehicles and batteries, opening the door for applications in
aerospace, military and automotive industries.
Natural materials, such as trabecular
bone and the toes of geckoes, have evolved with multiple levels 3-D
architectures spanning from the nanoscale to the macroscale. Human-made
materials have yet to achieve this delicate control of structural features.
"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."
The process Zheng and his collaborators
use to create the material is an innovation in a digital light 3-D printing
technique that overcomes current tradeoffs between high resolution and build
volume, a major limitation in scalability of current 3-D printed microlattices
and nanolattices.
Related materials that can be produced
at the nanoscale such as graphene sheets can be 100 times stronger than steel,
but trying to upsize these materials in three dimensions degrades their
strength eight orders of magnitude - in other words, they become 100 million
times less strong.
"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 added.
These multi-leveled hierarchical
lattice also means more surface area is available to collect photons energies
as they can enter the structure from all directions and be collected not just
on the surface, like traditional photovoltaic panels, but also inside the
lattice structure. One of the great opportunities this study creates is the
ability to produce multi-functional inorganic materials such as metals and
ceramics to explore photonic and energy harvesting properties in these new
materials
Besides Zheng, 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 the Department of Energy Lawrence Livermore
Laboratory-directed research support with additional support from Virginia
Tech, the SCHEV fund from the state of Virginia, and the Defense Advanced
Research Projects agency.
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