MIT - Page 4

Researchers at MIT have produced a catalog of the exact sizes and shapes of defects and holes that would most likely be observed (as opposed to the many more that are theoretically possible) when a given number of atoms is removed from the atomic lattice. The MIT team collaborated on this project with researchers at Lockheed Martin Space and Oxford University.

The 12 different forms that six-atom vacancy defects in graphene can have, as determined by the researchers

It’s been a longstanding problem in the graphene field, what we call the isomer cataloging problem for nanopores, Michael Strano from MIT says. "For those who want to use graphene or similar two-dimensional, sheet-like materials for applications including chemical separation or filtration", he says, we just need to understand the kinds of atomic defects that can occur, compared to the vastly larger number that are never seen".

Researchers from the U.S. Army, in collaboration with RDECOM Research Laboratory, the Army's corporate research laboratory (ARL), Stanford University, MIT, University of Southern California and Argonne National Laboratory, have discovered a way to get more energy out of energetic materials containing aluminum, common in battlefield systems, by igniting aluminum micron powders coated with graphene oxide. This research could lead to enhanced energetic performance of metal powders as propellant/explosive ingredients in Army's munitions.

This discovery makes use of graphene oxide as an effective light-weight additive for practical energetic applications using micron-size aluminum powders (µAl), i.e., aluminum particles one millionth of a meter in diameter.

An international research team, co-led by researchers at the University of California, Riverside, which also included researchers at MIT, Nanyang Technological University, Singapore; Institute of High Performance Computing, Singapore; UC Berkeley; and National Institute for Materials Science, Japan, has found a new mechanism for highly-efficient charge and energy flow in graphene, opening the door to new types of light-harvesting devices.

The researchers made pristine graphene into different geometric shapes, connecting narrow ribbons and crosses to wide open rectangular regions. They found that when light illuminated constricted areas, such as the region where a narrow ribbon connected two wide regions, a large light-induced current, or photocurrent, was detected.

MIT engineers recently managed to create cell-sized robots that could collect data about their environment, but were quite tricky to manufacture. Now, the team has found a way to mass produce these synthetic cells (syncells) through controlled fracturing of graphene.

The previously developed MIT robots were so small, that there was no point trying to steer them, but they could still sense and observe, scanning their surroundings and storing data for long periods of time. Later, they could be filtered out and analyzed to get a reading of water quality, for example, or biomarkers for disease in a patient's bloodstream.

MIT recently received $1,500,000 in funding from the U.S. Department of Energy for its project titled "Low-Cost, High-Efficiency III-V Photovoltaics Enabled By Remote Epitaxy through Graphene"

This funding was a part of the Solar Energy Technologies Office Fiscal Year 2018 (SETO FY2018) funding program, which addresses the affordability, flexibility, and performance of solar technologies. The total funding was $53 million for 53 projects.

Researchers at MIT have found a way to directly pinprick microscopic holes into graphene as the material is grown in the lab. Using this technique, they have fabricated relatively large sheets of graphene (roughly the size of a postage stamp), with pores that could make filtering certain molecules out of solutions vastly more efficient.

Holes would typically be considered unwanted defects, but the MIT team has found that certain defects in graphene can be an advantage in fields such as dialysis. Typically, much thicker polymer membranes are used in laboratories to filter out specific molecules from solution, such as proteins, amino acids, chemicals, and salts. If it could be tailored with selectively-sized pores that let through certain molecules but not others, graphene could substantially improve separation membrane technology.

MIT and Graphenea have developed an array of graphene sensors for sensitive and selective detection of ammonia. The array consists of 160 graphene pixels, allowing large statistics that result in improved sensing performance. The sensors are extensively tested for various real-life operational conditions, which seems to be a step forward to practical use.

The sensors are built by attaching porphyrins, a class of organic molecules, to the graphene surface. Porphyrins are particularly well-matched to graphene sensors because they provide excellent sensitivity while producing minimal perturbation to graphene’s outstanding electrical properties. When ammonia molecules attach to porphyrins, the compound becomes a strong dipole that changes electrical properties of the graphene. This electrical change is detected as a sign of the presence of ammonia.

Researchers from Bilkent University and Izmir Institute of Technology in Turkey, MIT and University of Manchester have developed a system that can reconfigure its thermal appearance to blend in with varying temperatures in a matter of seconds.

Previously, scientists have tried to develop thermal camouflage for various applications, but they have encountered problems such as slow response speed, lack of adaptability to different temperatures and the requirement for rigid materials. The team in this research wanted to develop a fast, rapidly adaptable and flexible material.

A team of researchers at MIT, Raytheon BBN Technologies and Columbia University have used graphene to design a fast yet highly sensitive bolometer that can work at room temperature and may even be less expensive. Bolometers are devices that monitor electromagnetic radiation through heating of an absorbing material. Most such devices have limited bandwidth and must be operated at ultralow temperatures, which damages their usefulness.

The findings of this work could help pave the way toward new kinds of astronomical observatories for long-wavelength emissions, new heat sensors for buildings, and even new kinds of quantum sensing and information processing devices, the multidisciplinary research team says.

Researchers at MIT and Israel's Technion have used graphene to devise a new way of enhancing the interactions between light and matter, in a work that could someday lead to more efficient solar cells that collect a wider range of light wavelengths, and new kinds of lasers and light-emitting diodes (LEDs) that could have fully tunable color emissions.

The basic principle behind the new approach is a way to get the momentum of light particles (photons) to more closely match that of electrons, which is normally much greater. This huge difference in momentum normally causes these particles to interact very weakly; bringing their momenta closer together enables much greater control over their interactions, which could enable new kinds of basic research on these processes as well as a host of new applications, the researchers say.