Glass Nanolattice Structures Four Times Strength but Five Times Lower in Density than Steel

By building a structure out of DNA and then coating it with glass, a research team led by Oleg Gang has created a very strong material with very low density.Gang and colleagues report that by building a structure out of DNA and then coating it with glass, they have created a very strong material with very low density. Glass might seem a surprising choice, as it shatters easily. However, glass usually shatters because of a flaw–such as a crack, scratch, or missing atoms–in its structure. A flawless cubic centimeter of glass can withstand 10 tons of pressure, more than three times the pressure that imploded the Oceangate Titan submersible near the Titanic this summer.

It’s very difficult to create a large piece of glass without flaws. But the researchers knew how to make very small flawless pieces. As long as glass is less than a micrometer thick, it’s almost always flawless. And since the density of glass is much lower than metals and ceramics, any structures made of flawless nano-sized glass should be strong and lightweight.

The glass only just coated the strands of DNA, leaving a large part of the material volume as empty space, much like the rooms within a house or building. The DNA skeleton reinforced the thin, flawless coating of glass making the material very strong, and the voids comprising most of the material’s volume made it lightweight. As a result, glass nanolattice structures are four times higher in strength but five times lower in density than steel. This unusual combination of lightweight and high strength has never been achieved before.

Materials that are both strong and lightweight could improve everything from cars to body armor. But usually, the two qualities are mutually exclusive. Now, researchers from Columbia Engineering, University of Connecticut (UConn), and Brookhaven National Lab (BNL) have developed an extraordinarily strong, lightweight material using two unlikely building blocks: DNA and glass.

“An ability to structure materials into prescribed architectures at nanoscale was envisioned as a way to enhance its mechanical properties, but there is no easy way to build at such small scales. Our DNA-based self-assembly strategy now demonstrates that it is possible,” says Oleg Gang, professor of chemical engineering and of applied physics and materials science at Columbia Engineering and a scientist at BNL who directed the work published July 19 in Cell Reports Physical Science.

Highlights


• Fabrication of 3D silica nanostructures via DNA assembly and templating


• In situ micro-compression testing to examine the mechanical properties


• Nanostructures show a nearly theoretical compressive strength of 5 GPa

Summary


Continuous nanolattices are an emerging class of mechanical metamaterials that are highly attractive due to their superior strength-to-weight ratios, which originate from their spatial architectures and nanoscale-sized elements possessing near-theoretical strength. Rational design of frameworks remains challenging below 50 nm because of limited methods to arrange small elements into complex architectures. Here, we fabricate silica frameworks with ∼4- to 20-nm-thick elements using self-assembly and silica templating of DNA origami nanolattices and perform in situ micro-compression testing to examine the mechanical properties. We observe strong effects of lattice dimensions on yield strength and failure mode. Silica nanolattices are found to exhibit yield strengths higher than those of any known engineering materials with similar mass density. The robust coordination of the nanothin and strong silica elements leads to the combination of lightweight and high-strength framework materials offering an effective strategy for the fabrication of nanoarchitected materials with superior mechanical properties.

“For the given density, our material is the strongest known,” says Seok-Woo Lee, a materials scientist at UConn who co-directed the study.

Strength is relative. Iron, for example, can take seven tons of pressure per square centimeter. But it’s also very dense and heavy, weighing 7.8 grams/cubic centimeter. Other metals, such as titanium, are stronger and lighter than iron. And certain alloys combining multiple elements are even stronger. Strong, lightweight materials have allowed for lightweight body armor, better medical devices, and made safer, faster cars and airplanes. The easiest way to extend the range of an electric vehicle, for example, is not to enlarge the battery but rather make the vehicle itself lighter without sacrificing safety and lifetime. But traditional metallurgical techniques have reached a limit in recent years, and materials scientists have had to get even more creative to develop new lightweight high-strength materials.

Materials scientists from Columbia Engineering, UConn, and BNL built an exceptionally strong, lightweight material out of DNA scaffold that allowed the formation of nanostructured silica, a glass-like material. The series of images at the top (A) shows how the skeleton of the structure is assembled with DNA, then coated with glass. (B) shows a transmission electron microscope image of the material, and (C) shows a scanning electron microscope image of it, with the two right-hand panels zooming in to features at different scales.