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

Despite advancements in cooling solutions, the interface between an electronic chip and its cooling system has remained a barrier for thermal transport due to the materials' intrinsic roughness. Now, researchers from Carnegie Mellon University and the Massachusetts Institute of Technology have built a flexible, powerful, and highly reliable material to efficiently fill the gap. The material is composed of two thin copper films with a graphene-coated copper nanowire array sandwiched in between. The sandwich material consists of a thermal interface material that has twice the thermal conductance of current state-of-the-art thermal interface materials.

Researchers from Florida State University and BNNT Materials (Newport News, VA) have completed the first-ever study on how purified boron nitride nanotubes remain stable in extreme temperatures in inert environments. Boron nitride nanotubes are stronger and more resistant to high temperatures than carbon nanotubes, but manufacturing these materials is challenging. The researchers found that boron nitride nanotubes are fully stable at up to 1,800 degrees Celsius in an inert environment, the chemically inactive atmosphere in which they are manufactured. 

Researchers from Pennsylvania State University and McMaster University in Canada have created two-dimensional oxides, materials with special properties that can serve as an atomically thin insulating layer between layers of electrically conducting materials. The oxides showed good properties for use in stacked materials called heterostructures that can enable electrons to travel vertically through the structure instead of horizontally like conventional electronic devices.

Researchers from the Massachusetts Institute of Technology, the Georgia Institute of Technology, the University of Virginia, Washington University in St. Louis, Sejong University (Seoul, South Korea), Yonsei University (Seoul, South Korea) have developed a new process based on two-dimensional (2D) materials to create light-emitting diode (LED) displays with smaller and thinner pixels. The study shows that the world's thinnest and smallest pixeled displays can be enabled by an active layer separation technology using 2D materials, such as graphene and boron, to enable high array density micro-LEDs.

Scientists from the U.S. Department of Energy’s Lawrence Livermore National Laboratory, Sandia National Laboratories, and Lawrence Berkeley National Laboratory, as well as the Indian Institute of Technology in Gandhinagar, India, have created 3–4 nanometer ultrathin nanosheets of a metal hydride that increase hydrogen storage capacity. Hydrogen has the highest energy density of any fuel and is considered a viable solution for ground transportation, aircraft, and marine vessels. The material created in this most recent collaboration came from solvent-free mechanical exfoliation in zirconia, yielding a material that is only 11–12 atomic layers thick and can hydrogenate to about 50 times the capacity of the bulk material.

Researchers from the U.S. Department of Energy’s SLAC National Accelerator Laboratory and Argonne National Laboratory, as well as Stanford University, Cornell University, the University of California, Berkeley, North Carolina State University, the University of Arkansas, and the University of Toulouse in France have discovered a size threshold beyond which antiferroelectric materials lose those properties, becoming ferroelectric. To explore how an antiferroelectric material's properties may change at small scales, the researchers focused on lead-free sodium niobate membranes. “We found that when [these] membranes were thinner than 40 nm, they become completely ferroelectric,” said Ruijuan Xu, one of the scientists involved in this work. “And from 40 nm to 164 nm, we found that the material had some regions that were ferroelectric, while other regions were antiferroelectric."

Researchers at Yale University have discovered surprising wire-like properties of a protein made by electricity-producing bacteria that show similarity to those of methane-eating microbes. This protein nanowire allows bacteria to produce to highest electric power reported possible so far and explains how these bacteria can survive without oxygen-like membrane-ingestible molecules. But to date, no one had discovered how they are made and why they are so conductive. Using high-resolution cryo-electron microscopy, the researchers were able to see the nanowire's atomic structure.

Scientists from Rice University, Reading Hospital (West Reading, PA), and Fundación de Investigación Sanitaria de las Islas Baleares (Palma, Spain) have shown that molecular machines that are effective against antibiotic-resistant infectious bacteria and cancer cells can also kill infectious fungi. Based on the work of Nobel laureate Bernard Feringa, the scientists’ molecular machines are nanoscale compounds whose paddlelike chain of atoms moves in a single direction when exposed to visible light. This causes a drilling motion that allows the machines to bore into the surface of cells, killing them.

With some careful twisting and stacking, physicists at the Massachusetts Institute of Technology and the National Institute for Materials Science in Tsukuba, Japan, have revealed a new and exotic property in magic-angle graphene: superconductivity that can be turned on and off with an electric pulse, much like a light switch. The discovery could lead to ultrafast, energy-efficient superconducting transistors for neuromorphic devices – electronics designed to operate in a way similar to the rapid on/off firing of neurons in the human brain. Magic-angle graphene refers to a very particular stacking of graphene – an atom-thin material made from carbon atoms that are linked in a hexagonal pattern resembling chicken wire. 

Researchers at Northwestern University have developed a new way to significantly increase the potency of almost any vaccine. The scientists used chemistry and nanotechnology to change the structural location of adjuvants and antigens on and within a nanoscale vaccine, greatly increasing vaccine performance. The antigen targets the immune system, and the adjuvant is a stimulator that increases the effectiveness of the antigen.