A research group at CalTech is proving big and heavy materials are not the only ways to build strong, robust structures. By scaling the structure of materials down to the nanoscale, just billionths of a meter in size, it's possible to make structures that are lightweight, resilient, and more than 99% air. "Nanotechnology: Super Small Science" is produced by NBC Learn in partnership with the National Science Foundation.
Nanotechnology -- Nanoarchitecture
KATE SNOW, reporting:
The Eiffel Tower in Paris. The Statue of Liberty in New York. The Space Needle in Seattle. These massive structures were built with strong, heavy materials that can withstand the forces of nature and endure the test of time. But one scientist is proving that big and heavy are not the only ways to get strong, robust structures. By scaling the structure of materials down to the nanoscale, just billionths of a meter in size, it's possible to build structures that are lightweight and resilient, and are more than 99 percent air.
JULIA GREER (California Institute of Technology): We really like defying theories because we're all about breaking the rules.
SNOW: Julia Greer is a professor of materials science and mechanics at the California Institute of Technology and is funded by the National Science Foundation. Her research group is responsible for making the seemingly impossible possible by fabricating what she calls nano-metamaterials, microscopic building materials with nanoscale architecture inside that are light as a feather, but strong as steel.
GREER: We make these architected nano-metamaterials, so to speak, because they're not really only materials and they're not really only structures, they're both and that's a new field.
SNOW: Scientists are already designing metamaterials that can bend light to camouflage objects, improve wireless charging and manipulate sound waves for soundproofing. But Greer's team is one of the first to create structural metamaterials, made of anything from metal to ceramics. Their incredible strength is a result of how they're constructed. Greer uses a technique that can be seen throughout nature called hierarchical architecture. It's why a turtle's shell is so durable or a lobster's claw so strong. At the nanoscale, hierarchical architecture consists of complex, repeating patterns all invisible to the naked eye.
GREER: These hard biological materials have these kinds of levels of hierarchy, as we call them, in their design, which is they're never continuous. Evolution has had millions of years to arrive to that particular structure. So what we do with our architectures is we are inspired by the same approach.
SNOW: To test the strength of a certain material for a structural application, Greer's students use hierarchical architecture to design a 3-dimensional nanolattice, an open-air structure made out of individual hollow nanotubes with walls just tens to hundreds of nanometers thick. The nanolattice is printed as a polymer on the surface of a silicon wafer using a technique called two-photon lithography, a process similar to 3D laser printing in that they both can produce 3-dimensional objects. The nanolattice is then coated with the particular material, in this case, glass. After cutting the structure open with an ion beam, it is then left in a vacuum to completely remove the polymer, resulting in a hollow glass nanolattice. This one has a height of just 75,000 nanometers, about the diameter of a single human hair.
GREER: Oh it's definitely deforming, look at that! In the middle it's breaking on the sides.
SNOW: In this demonstration, Greer's team tests the strength of the nanolattice by placing it in an instrument they call a SEMentor. When the nanolattice is compressed, not only does it not collapse catastrophically.
GREER: Look at that. Totally didn't break.
SNOW: Something else unexpected happens.
GREER: Oh wow! That was the exciting part! Wow, did you see that? It's doing exactly the opposite of what it ought to be doing. This material is very brittle. It's just like a window glass, right? And so no matter which way you architect a window glass, you can imagine these little glass figurines, right? They should shatter when you push on them and this one apparently refuses to shatter no matter what.
SNOW: The design of the structure is the reason for its remarkable strength. As a result, scientists hope it might one day be possible to build a nearly indestructible car, an airplane so lightweight that you could easily pick it up.
ENGINEER: And liftoff!
SNOW: Or a rocket that could transport astronauts and cargo into space at a much cheaper cost. Greer's next challenge is scaling these nano-metamaterials up so that they can be manufactured in mass quantities and used in biomedical, military, and energy applications.
GREER: We're really shifting the way we think about materials. Up to this point, it's always been if you want something that's really strong or you want something that's damage tolerant, you know what to use because you know this is a metal. And what we're showing the world, at this point, is that you don't have to do that. You can dictate what the properties that you need are.
SNOW: For Greer, the nanotechnology that her team is developing is changing traditional thought around materials science, engineering and design.
GREER: It's no longer just the material properties that dictate the structure. We now have this concept of architecture and size which are tunable design parameters which have never existed before.
SNOW: Nanomaterials just billionths of a meter in size teaching us to expect the unexpected when it comes to architecture and design.
In "Avengers: Infinity War," the latest superhero smash-em-up, Captain America, Iron Man and company face off against villain Thanos. Thanos is the baddest of the bad guys to swagger on-screen in 10 years of Marvel blockbusters. Joe Russo, who co-directed the movie with his brother Anthony, told The Washington Post earlier in May that Thanos is "the Genghis Khan of this universe" with a philosophical bent.
Nanotechnology, "Nanotechnology: Super Small Science", Architecture, Materials, Structures, Strength, Lightweight, Weight, Composition, CalTech, California Institute of Technology, Julia Greer, Nanoscale, Nano-Metamaterials, Metamaterials, Construction, Hierarchical Architecture, Hierarchy, Nanolattice, Nanotube, Design, Materials Science, Engineering, National Science Foundation, NSF, Nanoarchitecture