News from the NNI Community - Research Advances Funded by Agencies Participating in the NNI

Designing new nanomaterials is an important aspect of developing next-generation devices used in electronics, sensors, energy harvesting and storage, and optical detectors. To design such nanomaterials, researchers create interatomic potentials through atomistic modeling, a computational approach that predicts how these materials behave by accounting for their properties at the smallest level. Now, researchers at Northwestern University have developed a new framework using machine learning that improves the accuracy of interatomic potentials in new materials design. The findings could lead to more accurate predictions of how new materials transfer heat, deform, and fail at the atomic scale.

Researchers have discovered a "layer" Hall effect in a solid state chip constructed of antiferromagnetic manganese bismuth telluride, a finding that signals a much sought-after topological Axion insulating state. Researchers believe that when it is fully understood, topological Axion insulators can be used to make semiconductors with potential applications in electronic devices. The material (antiferromagnetic manganese bismuth telluride) forms a two-dimensional layered crystal structure, which allowed the researchers to mechanically exfoliate atom-thick flakes using cellophane tape. Thin flake structures with even numbers of layers were proposed to be an Axion insulator.

Physicists at MIT have observed signs of a rare type of superconductivity in a material called magic-angle twisted trilayer graphene. The researchers report that the material exhibits superconductivity at surprisingly high magnetic fields of up to 10 Tesla, which is three times higher than what the material is predicted to endure if it were a conventional superconductor. The results strongly imply that magic-angle trilayer graphene is a very rare type of superconductor that is impervious to high magnetic fields. Such exotic superconductors could vastly improve technologies such as magnetic resonance imaging (MRI). MRI machines are currently limited to magnet fields of 1 to 3 Tesla. 

The magnetic component of today's memory devices is typically made of magnetic thin films. But at the atomic level, these magnetic films are still three-dimensional – hundreds or thousands of atoms thick. For decades, researchers have searched for ways to make thinner and smaller 2D magnets and thus enable data to be stored at a much higher density. Now, scientists at the University of California, Berkeley, and the U.S. Department of Energy's Lawrence Berkeley National Laboratory have developed an ultrathin 2D magnet that operates at room temperature and could lead to new applications in computing and electronics – such as high-density, compact spintronic memory devices – and new tools for the study of quantum physics.

For decades, researchers have searched for ways to use solar power to generate the key reaction for producing hydrogen as a clean energy source—splitting water molecules to form hydrogen and oxygen. But such efforts have mostly failed because doing it well was too costly, and trying to do it at a low cost led to poor performance. Now, researchers from The University of Texas at Austin have found a low-cost way to solve one half of the equation, using sunlight to efficiently split off oxygen molecules from water. The key to this breakthrough came through a method of creating electrically conductive paths through a thick silicon dioxide layer that involves arrays of nanoscale "spikes" of aluminum and that can be performed at low cost and scaled to high manufacturing volumes.

Most of the tests that doctors use to diagnose cancer are based on imaging. Cancer can also be found with molecular diagnostics, which can detect specific cancer-associated molecules that circulate in bodily fluids, such as blood and urine. Now, engineers at MIT have created a new diagnostic nanoparticle that combines both of these features: It can reveal the presence of cancerous proteins through a urine test, and it functions as an imaging agent, pinpointing the tumor location.

Current biological treatments for autoimmune diseases consist of monoclonal antibodies that search out and destroy factors in the immune system, such as the tumor necrosis factor, that mistakenly mount immune attacks against the body. But these treatments often have side effects and can have varying degrees of effectiveness in different individuals. Now, engineers at Duke University have built nanostructures which chemically tether protein subunits that can stimulate the type of biological response necessary to sequester the disease-causing excess of tumor necrosis factor.

Using a pioneering imaging technique, researchers at Cornell University have obtained a high-resolution snapshot of how ligands – molecules that bind to other molecules or metals – interact with the surface of nanoparticles. In doing so, the researchers made an unexpected discovery: They determined that by varying the concentration of an individual ligand, they could control the shape of the particle to which it is attached. This approach could result in chemical sensors that are sensitive at a very low level to a specific chemical in the environment.

One of the main drivers of antimicrobial resistance is the misuse and overuse of antimicrobial agents, which includes silver nanoparticles, an advanced material with well-documented antimicrobial properties. Now, researchers at the University of Pittsburgh have used laboratory strains of E. coli to better understand bacterial resistance to silver nanoparticles. The researchers sequenced the genome of the E. coli that had been exposed to silver nanoparticles and found a mutation in a gene that corresponds to an efflux pump that pushes heavy metal ions out of the cell.

Optical singularities typically occur when the phase of light with a specific wavelength is undefined. These regions appear completely dark. Today, some optical singularities, including optical vortices, are being explored for use in optical communications and particle manipulation, but scientists are just beginning to understand the potential of these systems. Now, researchers from Harvard University have developed a new technique to control and shape optical singularities. To demonstrate their technique, the researchers created a singularity sheet in the shape of a heart by using flat metasurfaces with precisely shaped nanopillars to shape the singularities.