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

A key step toward reusing carbon dioxide to make sustainable fuels is chaining carbon atoms together, and an artificial photosynthesis system developed at the University of Michigan can bind two of them into hydrocarbons. The system produces ethylene – a hydrocarbon typically used in plastics – with efficiency, yield, and longevity above other artificial photosynthesis systems. The device absorbs light through two kinds of semiconductors: a forest of gallium nitride nanowires, each just 50 nanometers wide, and the silicon base on which they were grown. The reaction transforming water and carbon dioxide into ethylene takes place on copper clusters that dot the nanowires.

Researchers have developed an innovative nanofibrous membrane to remove microplastics from drinking water. Water filters on the market today can remove some contaminants, but they’re not designed to capture microplastics. The filter membrane is made from polyvinyl alcohol fibers, which are polymers currently used in biomedical applications. The team chose the material because it is low-cost and is not toxic to humans, animals, or plants. “The idea is to design a filter that can be attached to a faucet so it can remove microplastic and lead at the same time from tap water,” said Maryam Salehi, one of the researchers involved in this study. 

Researchers from the U.S. Department of Energy's Pacific Northwest National Laboratory and Lawrence Berkeley National Laboratory; the University of Washington; North Carolina State University; and Xiamen University in China have achieved a uniform two-dimensional (2D) layer of silk protein fragments on graphene, a carbon-based material useful for its excellent electrical conductivity. This combination of materials—silk-on-graphene—could form a sensitive, tunable transistor highly desired by the microelectronics industry for wearable and implantable health sensors. The researchers also see potential for their use as a key component of memory transistors or “memristors,” in computing neural networks. Memristors allow computers to mimic how the human brain functions. 

Researchers at the University of Minnesota and the University of Arizona have provided new insights into how next-generation electronics break down or degrade over time. Using a sophisticated electron microscope, the researchers looked at the nanopillars within magnetic tunnel junctions – the building blocks for the non-volatile memory in smart watches and in-memory computing. The researchers ran a current through the device to see how it operates. As they increased the current, they were able to observe how the device degrades and eventually dies in real time. “What was unusual with this discovery is that we observed this burn out at a much lower temperature than what previous research thought was possible,” said Andre Mkhoyan, one of the scientists involved in this research.

Researchers from the University of Pennsylvania have demonstrated a new kind of nanopore platform that consists of two or more nanopores stacked just nanometers apart, allowing for more precise detection and control of DNA as it wiggles through. “With current platforms, when molecules like DNA are placed near the nanopores, it’s sort of like having spaghetti in a pot—tangled and difficult to work with, let alone guiding through one hole,” explains Dimitri Monos, one of the scientists involved in this study. “So, typically, researchers need to use proteins to capture, unwind, and straighten it, which, while effective, has many limitations. But with this new design, we’re essentially guiding molecules through two coupled nanopores in the material, providing a controlled, smoother passage of molecules.”

The National Institute for Occupational Safety and Health’s Nanotechnology Research Center (NTRC) is celebrating its 20-year anniversary! Over the years, researchers at the NTRC have studied the #toxicity of many engineered nanomaterials throughout their life cycles. The research has covered primary manufactured forms (such as carbon nanotubes, nanoscale titanium dioxide, and silver nanoparticles) and modified versions for specific applications (such as silica-coated iron oxide, heat-treated carbon nanotubes, and reduced graphene oxide). Early studies focused on the tiniest components of air pollution, known as ultrafine particles, which laid the foundation for ongoing research efforts to assess two types of nanoparticles found in workplaces: engineered nanomaterials (purposely created for various applications) and process-derived nanoparticles (unintentionally produced during industrial processes). Also, using samples from worker health effects studies, researchers developed toxicology studies to determine biomarkers of exposure and disease. Together, these studies offer valuable data for understanding workplace hazards and risks. 

Researchers at the University of Chicago Medicine Comprehensive Cancer Center have developed a nanomedicine that increases the penetration and accumulation of chemotherapy drugs in tumor tissues and effectively kills cancer cells in mice. The researchers looked at a particular pathway known as stimulator of interferon genes (STING), whose activation increases the leakiness of blood vessels near the tumor. They designed nanoparticles that encapsulates both STING activators and chemotherapy drugs and evaluated the antitumor effects of the therapy in multiple kinds of tumors in mice; they found large tumor growth inhibition and high cure rates.

Researchers from Duke University, the University of California, Los Angeles, the Icahn School of Medicine at Mount Sinai, and Harvard Medical School have developed a platform that uses sound waves as acoustic tweezers to sort viruses from other compounds in a liquid. The platform consists of a rectangular chip with a sample-loading inlet at one end and separate virus and waste outlets at the other end. Two acoustic beams were applied across the chip, perpendicular to the sample flow. Particles larger than 150 nanometers (nm) in diameter were trapped on the chip, particles smaller than 50 nm left through the waste outlet, and viruses of intermediate sizes (50 to 150 nm) were collected via the virus outlet.

A team of scientists from the U.S. Department of Energy's Oak Ridge National Laboratory and the University of Maine has identified and successfully demonstrated a new method to process a plant-based material, called nanocellulose, that reduced energy needs by a whopping 21%. The approach was discovered using molecular simulations that were run on the lab's supercomputers, followed by pilot testing and analysis. The method can significantly lower the production cost of nanocellulosic fiber and supports the development of a circular bioeconomy, in which renewable, biodegradable materials replace petroleum-based resources.

Researchers at the Massachusetts Institute of Technology have developed a new filtration material that might provide a nature-based solution to water contaminated by “forever chemicals,” or per- and poly-fluoroalkyl substances (PFAS). The filtration material, based on natural silk and cellulose, can remove a variety of these persistent chemicals, as well as heavy metals. The researchers devised a way of processing silk proteins into uniform nanoscale crystals, or “nanofibrils.” Then, they integrated cellulose into the silk-based fibrils, which formed a thin membrane that was highly effective at removing PFAS in lab tests.