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

Researchers from the Massachusetts Institute of Technology and the University of Udine in Italy have created a new type of three-dimensional transistor using a unique set of ultrathin semiconductor materials. It features vertical nanowires only a few nanometers wide, which can deliver performance comparable to state-of-the-art silicon transistors while operating efficiently at much lower voltages than conventional devices. The transistor’s extremely small size would enable more of these 3D transistors to be packed onto a computer chip, resulting in fast, powerful electronics that are also more energy-efficient. “This is a technology with the potential to replace silicon, so you could use it with all the functions that silicon currently has, but with much better energy efficiency,” says Yanjie Shao, the scientist who led this study.

Flame aerosol synthesis is used to create nanoparticles that serve as key ingredients in inks and air filters. While effective, this technique has limitations, including challenges with manipulating the flame, achieving precise control over the size and distribution of nanoparticles, and cost. Two new studies, from researchers at the University at Buffalo; the U.S. Department of Energy’s Lawrence Berkeley National Laboratory, Brookhaven National Laboratory, and Lawrence Livermore National Laboratory; and the National Synchrotron Radiation Research Centre in Taiwan have addressed these shortcomings. The studies center on a unique flame aerosol system that is versatile, easy-to-use and cost-effective. In one of the studies, the system was used to create metal-organic frameworks, which are porous nanomaterials; in the other study, the researchers showed that the system could be used to create high-entropy ceramic nanomaterials.

Cornell University researchers have made headway into understanding how twisted bilayer graphene becomes a superconductor. In 2023, the scientists developed a theoretical formalism to compute the highest possible superconducting transition temperature in any material obtained by stacking and twisting two-dimensional materials. For the current work, the scientists applied this theoretical formalism to twisted bilayer graphene. “One of the remarkable properties of twisted bilayer graphene is the associated tunability,” said Debanjan Chowdhury, one of the scientists involved in this study. “You have unprecedented control over temperature and the twist angle – the tiny electric fields that are applied to switch the material from being an insulator versus a superconductor – making it very easy to explore all sorts of exciting regimes in this material.”

Researchers from Drexel University, the University of Pennsylvania, and Accenture Labs (San Francisco, CA), and Corporal Michael J. Crescenz Veterans Affairs Medical Center (Philadelphia, PA) have built a textile energy grid that can be wirelessly charged. The grid was printed on nonwoven cotton textiles with an ink composed of MXene, a type of nanomaterial that is both conductive and durable enough to withstand the folding, stretching, and washing that clothing endures. The proof-of-concept represents an important development for wearable technology, which, at present, requires complicated wiring and is limited by the use of rigid, bulky batteries that are not fully integrated into garments.

Researchers at William & Mary have measured the strength and stretchability of minuscule nanofibrils present in the silk spun by the southern house spider. The core of a spider silk strand is composed of two distinct warps that form helical loops around a central foundation fiber. The tiniest fibers, nanofibrils, are spun into a mesh that surrounds those supporting structures. The researchers found that the nanofibrils in the southern house spider’s silk could stretch 11 times their original length, more than twice the amount of any spider silk previously tested. "As amazing as spider silk as a whole is, looking at these tiny fibrils, they are even stretchier,” said Hannes Schniepp, one of the scientists involved in this study.

Researchers from Northwestern University and the University of California, Los Angeles, have developed a new strategy that prevents frost formation before it begins. The researchers discovered that tweaking the texture of any surface and adding a thin layer of graphene oxide prevents frost from forming on the surface for one week, or potentially even longer. This is 1,000 times longer than current, state-of-the-art anti-frosting surfaces. As an added bonus, the new scalable surface design also is resistant to cracks, scratches, and contamination.

Researchers at the Massachusetts Institute of Technology have designed tiny particles that can be implanted at a tumor site, where they deliver two types of therapy: heat and chemotherapy. In a study of mice, the researchers showed that this therapy completely eliminated tumors in most of the animals and significantly prolonged their survival. To create a microparticle that could deliver both of these treatments, the researchers combined an inorganic material called molybdenum disulfide nanosheets with one of two drugs: doxorubicin or violacein. To make the particles, molybdenum disulfide and the drug are mixed with a polymer called polycaprolactone and then dried into a film that can be pressed into microparticles of different shapes and sizes. Once injected into a tumor site, the particles remain there throughout the treatment, and an external near-infrared laser is used to heat up the particles. 

Researchers from the University of Nebraska-Lincoln and South Dakota School of Mines and Technology are exploring the physical properties of two-dimensional materials called MXenes. Previous research by the Nebraska team on other MXene materials revealed their n-type (electron-rich) character and decreased conductivity in response to light. In contrast, the new material is the first MXene with demonstrated p-type (electron-deficient) property and increasing conductivity under illumination. "Previously studied MXenes were all n-type, but now we demonstrate the first p-type MXene,” said Alexander Sinitskii, the scientist who led this study. “This should enable complex structures where complementary MXenes are used together to achieve new electronic functionalities."The researchers performed experiments at the Nebraska Center for Materials and Nanoscience, a user facility that is part of the National Science Foundation-funded National Nanotechnology Coordinated Infrastructure.

Researchers from the University of Chicago; the University of California, Berkeley; Northwestern University; the University of Colorado Boulder; and  the U.S. Department of Energy’s Argonne National Laboratory have developed a new technique for growing quantum dots – nanocrystals used in lasers, quantum light-emitting diode (QLED) televisions, and solar cells. The researchers replaced organic solvents typically used to create quantum dots with molten salt – literally superheated sodium chloride of the type sprinkled on baked potatoes. "Sodium chloride is not a liquid in your mind, but assume you heat it to such a crazy temperature that it becomes a liquid … [N]obody ever considered these liquids as media” for the synthesis of quantum dots, said Dmitri Talapin, one of the scientists involved in this study.

Researchers from Carnegie Mellon University and the Indian Institute of Technology Bombay in Mumbai, India, have linked the immune response caused by lipid nanoparticles to their lipid chemistry. They found that some lipid structures bind strongly to receptors and others bind weakly. The strong interactions trigger the receptor and ultimately the immune response. The findings will help engineers tailor immune responses when designing lipid nanoparticles for drug delivery. "For vaccines, we might want something that's more immunogenic, so that the vaccine responds better,” said Namit Chaudhary, one of the scientists involved in this study. “But if we are delivering something to the brain or the liver, for example, we might not want to evoke substantial immune responses that might cause toxicity."