Infrastructure and everyday materials

Engineers at the Massachusetts Institute of Technology have found a way to create a metamaterial that is both strong and stretchy. (A metamaterial is a synthetic material with microscopic structures that give it exceptional properties.) The key to the new material’s dual properties is a combination of stiff microscopic struts and a softer woven architecture. The researchers printed samples of the new metamaterial, each measuring in size from several square microns to several square millimeters.

Researchers from the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California, Los Angeles, have created a heat pump that consists of stacked layers of electrocaloric materials, which temporarily change temperature in response to an electric field. Six polymer film discs, each about an inch in diameter and coated with carbon nanotubes, serve as a heat pump, moving warmth from the layer closest to the heat source away to the outermost layer. The nanotubes function as conductors for the electric field that stimulates the material.

Researchers from the University of California, Davis, have developed a new technique to trap clusters of platinum atoms in nanoscale islands. Previous work had shown that platinum arranged in clusters of a few atoms on a surface makes a better hydrogenation catalyst than either single platinum atoms or larger nanoparticles of platinum. But such small clusters tend to clump easily into larger particles, losing efficiency.

In a Perspective article published in Nature Materials, two engineers at the Massachusetts Institute of Technology, Carlos Portela and James Surjadi, discuss key hurdles, opportunities, and future applications in the field of mechanical metamaterials. Metamaterials are artificially structured materials with properties not easily found in nature. With engineered three-dimensional geometries at the micro- and nanoscale, metamaterials achieve unique mechanical and physical properties with capabilities beyond those of conventional materials.

Researchers from Cornell University and the Army Research Laboratory have devised a new method for designing metals and alloys that can withstand extreme impacts. When a metallic material is struck at an extremely high speed, it immediately ruptures and fails. The reason for that failure is embrittlement – the material loses its ability to bend without breaking – when deformed rapidly.

Researchers at Washington University in St. Louis have developed ultra-thin materials, called metasurfaces, that can amplify and interact with light regardless of its polarization. The metasurfaces are made of tiny nanoantennas that can both amplify and control light in very precise ways and could replace conventional refractive surfaces in eyeglasses and smartphone lenses.

Researchers at North Carolina State University have demonstrated a new technique that uses light to tune the optical properties of quantum dots. The researchers placed green-emitting perovskite quantum dots in a solution containing either chlorine or iodine. The solution was then run through a microfluidic system that incorporated a light source. The microfluidic environment enabled precise reaction control by ensuring uniform light exposure across small solution volumes, approximately 10 microliters per reaction droplet.

Bright, twisted light can be produced with technology similar to an Edison light bulb, researchers at the University of Michigan have shown. Usually photons from a blackbody source (which is in thermodynamic equilibrium with its environment) are randomly polarized – their waves may oscillate along any axis. The new study revealed that if the emitter was twisted at the micro or nanoscale, with the length of each twist similar to the wavelength of the emitted light, the blackbody radiation would be twisted, too.

Researchers from Carnegie Mellon University have found a way to control the size and structure of active colloids while yielding more than 100 times the amount created by earlier fabrication methods. The team's active colloids are linked together using DNA nanostructures – an innovation that makes them flexible, agile, and responsive to signals in their environment. Typically, DNA nanotechnology can only be studied using expensive equipment.

Researchers from Northwestern University, Duke University, and Cornell University have developed the first two-dimensional mechanically interlocked material. Looking like the interlocking links in chainmail, the nanoscale material exhibits exceptional flexibility and strength. With further work, this material holds promise for use in high-performance, light-weight body armor and other uses that demand lightweight, flexible, and tough materials. "We made a completely new polymer structure," said William Dichtel, the study's corresponding author.