When scientists create a material, they have to decide how to balance strength and density. Improve one, and they have to dock the other.
At the Karlsruhe Institute of Technology in Germany, researchers found inspiration in a natural material: bone. Bone is light due to the air pockets it incorporates into its structure and, while not incredibly strong, it’s able to withstand a great deal of stress before breaking. The researchers published their work in Proceedings of the National Academy of Sciences on Monday.
The key to bones’ strength is that they are made of a repeating pattern. Light materials like foam have a random structure, which is why they collapse if any pressure is applied. The researchers tried a variety of patterns, including cubes, pyramids and honeycombs. They were able to use a lithography machine to create at least 10 different options made of a polymer covered in an aluminum compound. They found that some buckled under pressure while others fractured.
While researchers now have some options for printing bone-mimicking structures, you can’t print them on a home 3D printer just yet. The material requires a printer that’s accurate down to the single micron scale, and most desktop 3D printers don’t go past 100 microns (though the OWL Nano could change that). The researchers instead used 3D laser lithography, which much like stereolithography, uses a laser to cure a light-sensitive material.
MIT researchers did use bone as inspiration to create a fracture-resistant material last year, though at the scale a desktop 3D printer can print. They created a sheet of brick-like blocks that use a soft and more rigid material to lend both strength and flexibility. But it didn’t integrate a bone-like structure at a smaller scale. It’s theorized that if similar materials are someday built at the nanometer scale, they will become even stronger.