Image of the octet-truss sample used. Credit: Felice Frenkel.A team from MIT and the Lawrence Livermore National Laboratory (LLNL) in the US has developed a way to produce significantly stiff, strong and light structures with ultralow density at the microscale, and which can be fabricated from metals or polymers or other materials from available 3D printing technology. The new material is both ultrastiff and ultralight as it is based on microlattices that present nanoscale features, potentially benefiting aerospace and other transportation applications that depend on lightweight materials with high mechanical performance.
The new system, which was reported in Science [Zheng et al. Science (2014), DOI: 10.1126/science.1252291], was tested using three engineering materials – metal, ceramic and polymer – using a high-precision 3D printing process called projection microstereolithography that was developed by the two groups. They claim the resulting materials are extremely light in terms of density but with far superior mechanical properties due to the geometry of the lattice.
Although the geometric basis for such microstructures has been known for a few years, it took time to bring this understanding to a stage where it could be printed using digital projection. Stiffness and strength usually reduce with the density in a material, but these structures were shown to distribute and direct the loads so that a lighter structure could maintain its strength. As LLNL’s Christopher Spadaccini pointed out, “This material is among the lightest in the world. However, because of its microarchitected layout, it performs with four orders of magnitude higher stiffness than unstructured materials, like aerogels, at a comparable density.”
MIT’s Nicholas Fang agreed, “We found that for a material as light and sparse as aerogel, we see a mechanical stiffness that’s comparable to that of solid rubber, and 400 times stronger than a counterpart of similar density. Such samples can easily withstand a load of more than 160,000 times their own weight.”
Such materials could find uses in areas where the factors of high stiffness, high strength and reduced weight bring benefits. As the structures used in the aerospace industry rely on the amount of weight being carried being kept to a minimum, the advantages of these materials is obvious. There is also a need for such materials in smaller products, like batteries in portable devices, and with the materials being able to conduct sound and elastic waves very uniformly, they could be used in new acoustic metamaterials for efficient vibration isolation and impact absorption.