These multiscale metallic materials display super elasticity because of their designed hierarchical 3D architectural arrangement and nanoscale hollow tubes, resulting in more than a 400% increase of tensile elasticity over conventional lightweight metals and ceramic foams.
The approach, which produces multiple levels of 3D hierarchical lattices with nanoscale features, could be useful anywhere there's a need for a combination of stiffness, strength, low-weight and high flexibility - such as in structures to be deployed in space, flexible armours, lightweight vehicles and batteries.
“Creating 3D hierarchical micro features across the entire seven orders of magnitude in structural bandwidth in products is unprecedented,” said Xiaoyu Zheng, assistant professor of mechanical engineering. “Assembling nanoscale features into billets of materials through multi-levelled 3D architectures, you begin to see a variety of programmed mechanical properties such as minimal weight, maximum strength and super elasticity at centimetre scales.”
The process Zheng and his collaborators use to create the material is an innovation in a digital light 3D printing technique that overcomes current trade-offs between high resolution and build volume, a major limitation in scalability of current 3D 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.
“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-levelled hierarchical lattices also have a high surface area allowing them to collect more photons. The photons 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. This study has created the ability to explore photonic and energy harvesting properties in these new multi-functional inorganic materials.