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

Quantum dots are lab-grown nanoparticles with special optical properties that are detectable by standard microscopy, tomography, and fluorescence imaging. Now, scientists at the University of Illinois Urbana Champaign have used quantum dots to image macrophages – immune cells present in fat tissue – inside the body. The team created quantum dots coated with dextran, a sugar molecule that also targets macrophages in fat tissue. As a proof-of-concept, the scientists injected these quantum dots into obese mice and compared imaging results against dextran alone, the current standard for imaging macrophages. Quantum dots outperformed dextran alone across all imaging platforms, including simple optical techniques.

Scientists from the University of Chicago, Northwestern University, Arizona State University, the University of California, Berkeley, the U.S. Department of Energy’s Stanford Linear Accelerator Center and Lawrence Berkeley National Laboratory, and Technische Universität Dresden in Germany have laid out design rules to make nanocrystals work together. Scientists can grow nanocrystals out of many different materials, but whenever they try to assemble these nanocrystals together into arrays, the resulting crystals grow with long “hairs” around them. These hairs made it difficult for electrons to jump from one nanocrystal to another. The new method is meant to reduce the hairs around each nanocrystal, so they can be packed more tightly, allowing electrons – the messengers of electronic communication – to move easily along.

As part of an overarching quest to build “skin-inspired” electronics that are soft and stretchy, researchers at Stanford University have shown the proof of principle toward a stretchable, potentially reshapable display. About three years ago, the researchers discovered that a yellow-colored light-emitting polymer, called SuperYellow, not only became soft and pliable but also emitted brighter light when mixed with a type of polyurethane, a stretchy plastic. After adding polyurethane, the researchers saw that SuperYellow formed nanostructures that were connected like a fishnet and made the polymer emit brighter light.

Researchers from Harvard University and the University of Arizona have developed an attachment that can turn just about any camera or imaging system into polarization cameras. The attachment uses metasurfaces of subwavelength nanopillars to direct light based on its polarization and compiles an image that captures polarization. The researchers attached the polarization metasurface to an off-the-shelf machine vision camera, simply screwing it on in front of the objective lens. The attachment could be used to improve machine vision in vehicles or in biometric sensors for security applications.

Researchers at the University of Chicago have developed a new way to guide light in one direction on a tiny scale. By coupling light confined in a nanophotonic waveguide with an atomically thin, two-dimensional semiconductor, the researchers exploited the properties of both the light and the material to guide photons in one direction. The resulting small, tunable on-chip photonic interface could lead to smaller photonic integrated circuits that would be integrated into computing systems and self-driving cars.

Scientists at Stanford University have developed the first non-invasive technique for controlling targeted brain circuits in behaving animals from a distance. By artificially outfitting specific neurons in the brains of mice with a heat-sensitive molecule, the scientists found that it was possible to stimulate the modified cells by shining infrared light through the skull and scalp from up to a meter away. The new technique also relies on nanoparticles that can be injected into targeted brain regions to absorb and amplify the infrared light that is going through the brain tissue.

Physicists at MIT and elsewhere have revealed direct evidence of electron correlations – effects from the interaction felt between two negatively charged electrons – in a two-dimensional material called ABC trilayer graphene. In ABC trilayer graphene, three graphene sheets are stacked at the same angle and slightly offset from each other, like layered slices of cheese. An ABC trilayer graphene is similar to the more well-studied magic-angle bilayer graphene, in that both materials involve layers of graphene. Graphene is made from a lattice of carbon atoms arranged in a hexagonal pattern, similar to chicken wire. 

Researchers from the University of California, Irvine; the U.S. Department of Energy’s Brookhaven National Laboratory and Lawrence Livermore National Laboratory; Tokyo University of Agriculture and Technology; Okayama University; and Oxford Instruments Asylum Research have taken a close look at the ultrahard teeth of plant-eating invertebrates, called gumboot chitons, that use their teeth to scrape and grind algal deposits from coastal rocks. The researchers had previously found that these teeth are constructed of highly aligned magnetic nanorods, which provide strength and resistance. This time, the researchers showed, for the first time in natural systems, that at the early stages of tooth development, a pre-assembled organic fibrous material, called chitin, guided the formation of these nanorods via a highly ordered, mesocrystalline iron oxide known as ferrihydrite.

Researchers from MIT (including the Institute for Soldier Nanotechnologies), the U.S. Army Research Institute of Environmental Medicine, the Rhode Island School of Design, Case Western Reserve University, and the University of Wisconsin-Madison have designed an acoustic fabric that incorporates fibers that work like a microphone, converting sound into mechanical vibrations and then into electrical signals. The active layer of the fiber – a composite consisting of a piezoelectric polymer loaded with piezoelectric barium titanate nanoparticles – produces an electrical signal when the fiber is bent or mechanically deformed, providing a means for the fabric to convert sound vibrations into electrical signals.

Researchers from North Carolina State University and the University at Buffalo have developed and demonstrated a "self-driving lab" that uses artificial intelligence and fluidic systems to advance our understanding of metal halide perovskite nanocrystals. These nanocrystals are an emerging class of semiconductor materials that could be used in printed photonic devices and energy technologies. For example, the nanocrystals are efficient optically active materials and are under consideration for use in next-generation light-emitting diodes (LEDs).