In the realm of nanoscale science, researchers attain unmatched precision and insight in material manipulation. However, at larger scales, materials frequently contend with defects and contaminants that compromise their intricate structures, rendering them vulnerable to breakage. This fragility is notably apparent in various forms of glass, contributing to its reputation as a delicate material.
Scientists hailing from Columbia University, the University of Connecticut, and the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory have achieved a breakthrough by creating a pristine form of glass and encapsulating specialized DNA segments within it. The resulting material surpasses steel in strength while retaining an extraordinary lightness. Such a combination of qualities is rarely encountered in materials, and further exploration holds potential for groundbreaking applications in engineering and defense. Their findings have been documented in the journal “Cell Reports Physical Science.”
DNA: The Blueprint for Innovation
DNA, or deoxyribonucleic acid, carries biological instructions in living organisms, guiding cell formation, growth, and reproduction. DNA is classified as a polymer, belonging to a group of tough and elastic materials, including plastic and rubber. The remarkable properties of polymers have piqued the interest of material scientists, sparking numerous innovative experiments. Oleg Gang, a materials scientist at the Center for Functional Nanomaterials (CFN) and a professor at Columbia University, has been leveraging DNA’s unique attributes for material synthesis, resulting in a plethora of discoveries. This pioneering technology has led to a wide range of inventive applications, spanning from drug delivery to electronics.
Gang had previously collaborated with Brookhaven postdoctoral researcher Aaron Michelson, the lead author of the study, on an experiment involving DNA structures to construct a robust framework for novel materials. DNA molecules exhibit intriguing behavior, with individual nucleotides, the fundamental units of nucleic acids, determining bonding between complementary sequences. Precise control of these bonds allows scientists to engineer the folding of DNA into specific shapes, known as “origami.” These nanoscale DNA shapes serve as building blocks that can be programmed to “self-assemble” using addressable DNA bonds. This capability enables the spontaneous formation of well-defined structures with repetitive patterns.
These DNA blocks can then aggregate to create a larger lattice with a recurring pattern. This process empowers scientists to craft 3D-ordered nanomaterials from DNA and integrate inorganic nanoparticles and proteins, as demonstrated in previous studies by the team. After gaining mastery over this unique assembly process, Gang, Michelson, and their team embarked on exploring the potential of employing this biomolecular scaffolding to generate silica frameworks while preserving the scaffold’s architecture.
“We focused on using DNA as a programmable nanomaterial to form a complex 3D scaffold,” explained Michelson. “We wanted to explore how this scaffold would perform mechanically when translated into more stable solid-state materials, specifically by having this self-assembling material cast in silica, the primary constituent of glass.”
Michelson’s work in this field earned him the Robert Simon Memorial Prize at Columbia University. His exploration of DNA frameworks encompassed various characteristics and applications, ranging from mechanical properties to superconductivity. Much like the structures he has constructed, Michelson’s work continues to evolve and expand as it accumulates new layers of insight from these groundbreaking experiments.
The next phase of the fabrication process was inspired by biomineralization, a process in which certain living tissues produce minerals to enhance their hardness, such as bone formation.
“We were highly interested in investigating how we could improve the mechanical properties of conventional materials, like glass, by structuring them at the nanoscale,” Gang noted.
The researchers employed an extremely thin layer of silica glass, measuring only about 5 nanometers or a few hundred atoms in thickness, to coat the DNA frameworks. This left the inner spaces open, ensuring that the resulting material would be ultra-light. At this scale, the glass proved resistant to flaws or defects, endowing it with a strength not observed in larger glass pieces that tend to develop cracks and shatter. However, to precisely determine the strength of this material on such a minuscule scale, specialized equipment was required.
Resilience Under Microscopic Pressure
Assessing the sturdiness of objects is typically straightforward. Poking, prodding, and applying pressure to surfaces can offer valuable insights into their strength. These tactile examinations can reveal whether materials bend, creak, buckle, or remain steadfast under stress, even without precise measuring tools. But how does one evaluate the strength of an object that is too minuscule to see?
“To measure the strength of these tiny structures, we employed a technique called nanoindentation,” Michelson elucidated. “Nanoindentation is a mechanical test performed on a very small scale using a precise instrument capable of applying and measuring resistive forces. Our samples are only a few microns thick, roughly a thousandth of a millimeter, making conventional measurements impossible. By combining an electron microscope with nanoindentation, we can simultaneously gauge mechanical behavior and observe the compression process.”
As the diminutive device exerts pressure or indents the sample, researchers can take measurements and monitor the material’s mechanical properties. This approach also allows them to observe how the material behaves as the compression is released and the sample returns to its original state. Any cracks or structural failures that occur during this process can be meticulously recorded, providing invaluable data.
When put to the test, the glass-coated DNA lattice exhibited a strength four times greater than that of steel. Remarkably, its density was approximately five times lower. While there are materials known for their strength and relatively low weight, this level of achievement had not been previously attained.
This specific nanoindentation technique was not originally available at CFN.
“We collaborated with Seok-Woo Lee, an associate professor at the University of Connecticut, who specializes in the mechanical properties of materials,” Gang stated. “He was a CFN user who leveraged some of our capabilities and resources, such as electron microscopes, which is how we established a connection with him. Initially, we did not have the capability for nanoindentation, but he directed us to the appropriate tools and set us on the right path. This is another example of how collaborative efforts between scientists from academia and national laboratories yield significant benefits. We now possess the necessary tools and expertise to further advance studies like this.”
Constructing a Promising Future
While significant work remains before considering the scale-up and diverse applications of such a material, materials scientists have reason to be excited about the future implications. The research team intends to investigate other materials, such as carbide ceramics, which are even stronger than glass, to unravel their behavior and properties. This could pave the way for even stronger and lighter materials in the future.
Although Aaron Michelson’s career is still in its early stages, he has already achieved remarkable milestones and eagerly anticipates embarking on the next phases of his research.
“Becoming a postdoc at Brookhaven Lab is an incredible opportunity, especially after being a Columbia University student who frequently worked at the CFN,” Michelson recalled. “This led me to continue my journey as a postdoc. The capabilities available at CFN, particularly in the field of imaging, have significantly advanced my work.”
In conclusion, the fusion of DNA and glass at the nanoscale has opened doors to a new realm of material science, introducing a material that is stronger than steel yet astonishingly lightweight. This breakthrough not only underscores the extraordinary potential of nanoscale.
Reference: “High-strength, lightweight nano-architected silica” by Aaron Michelson, Tyler J. Flanagan, Seok-Woo Lee and Oleg Gang, 27 June 2023, Cell Reports Physical Science.
DOI: 10.1016/j.xcrp.2023.101475
Source: scitechdaily.com