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

Researchers at the University of Nebraska–Lincoln are one step closer to developing a new kind of transistor chip that harnesses the biological responses of living organisms to drive current through the device. The researchers have developed tiny networks of self-assembling necklaces made of gold nanoparticles (10 nanometers each). Each network spans about 25 micrometers, roughly a quarter of the diameter of a human hair. When connected, these networks serve as a conduit for current that can be regulated to form a transistor that is about 1,000 times more responsive to external stimuli than today’s most advanced metal transistors.

Researchers from Brown University and the University of Maryland have demonstrated a solid ion conductor that combines copper with cellulose nanofibrils, which are nanomaterials derived from wood. The paper-thin solid ion conductor has an ion conductivity that is 10 to 100 times better than other polymer ion conductors. It could be used as a solid battery electrolyte or as an ion-conducting binder for the cathode of an all-solid-state battery. 

Researchers have created tiny chip-based optical tweezers that can be used to optically levitate nanoparticles in a vacuum. Optical tweezers use a tightly focused laser beam to hold the nanoparticles. Usually, optical traps are produced with bulky optical components, but in this case, the on-chip optical levitation was realized with an ultrathin metalens. Accomplishing this feat in a vacuum helps improve the sensitivity of the system.

Researchers at Purdue University have shown that graphene's viscous fluid supports unidirectional electromagnetic waves on the edge. These "edge waves" are linked to a new topological phase of matter and symbolize a phase transition in the material, not unlike the transition from solid to liquid.

Scientists working at the Wyss Institute at Harvard University, the Blavatnik Institute at Harvard Medical School, and Boston Children’s Hospital have used DNA to create what may be the world’s tiniest ruler for measuring proteins. Dubbed DNA nanoswitch calipers, this technology enables researchers to perform distance measurements on single peptides (the building blocks of proteins) with high precision by applying small amounts of force. A DNA nanoswitch caliper is based on the underlying technology of the DNA nanoswitch: a single strand of DNA with molecular “handles” attached to it at multiple points along its length. 

The discovery in 2018 of superconductivity in two single-atom-thick layers of graphene stacked at a precise angle of 1.1 degrees (called “magic”-angle twisted bilayer graphene) came as a big surprise to the scientific community. Since the discovery, physicists have asked whether magic graphene's superconductivity can be understood using existing theory (conventional superconductors), or whether fundamentally new approaches are required (unconventional superconductors). Now, researchers at Princeton University have settled this debate by showing an uncanny resemblance between the superconductivity of magic graphene and that of high-temperature (or unconventional) superconductors. 

This article reviews research on twisted multilayer (bilayer, trilayer, and double bilayer) graphene by researchers at the University of Maryland’s Joint Quantum Institute and Condensed Matter Theory Center. The article provides historical context for this research and discusses theories developed by the researchers to explain the occurrence of superconductivity and magnetism in multilayer graphene.

The absence of a property called a band gap in graphene restricts its ability to function as a semiconductor. The dilemma has led scientists to explore ways to produce a band gap in graphene. One popular method has been to chemically modify the surface of graphene with hydrogen, a process called "hydrogenation." But the conventional way of doing this can seriously damage the surface of graphene within seconds or minutes. Now, scientists at Princeton University and the U.S. Department of Energy's Princeton Plasma Physics Laboratory have developed a novel method for hydrogenating graphene that uses low-temperature hydrogen plasma.

Researchers at Rice University have created nanostructures of silica with a sophisticated 3D printer, demonstrating a method to make electronic, mechanical, and photonic micro-scale devices from the bottom up. The printing process required the researchers to develop a unique ink by creating resins that contain nanospheres of silicon dioxide doped with polyethylene glycol to make them soluble.

Researchers at Harvard University, MIT, and the National Institute for Materials Science in Japan have carried out a study aimed at investigating Chern insulator ground states in twisted bilayer graphene. In Chern insulator ground states, the bulk of the material is insulating, yet electrons can propagate along the edges without dissipating heat. The researchers provide evidence of the existence of a sequence of incompressible states with unpredicted Chern numbers in twisted bilayer graphene.