MIT team reports new roll-to-roll process for production of large sheets of high-quality graphene

Researchers at MIT have developed a new roll-to-roll production process for large sheets of high-quality graphene, which the team says could lead to ultra-lightweight, flexible solar cells, and to new classes of light-emitting devices and other thin-film electronics.

MIT develops roll-to-roll process for graphene production image

The new manufacturing process, which the team says should be relatively easy to scale up for industrial production, involves an intermediate “buffer” layer of material that is key to the technique’s success. The buffer allows the ultrathin graphene sheet, less than a nanometer (billionth of a meter) thick, to be easily lifted off from its substrate, allowing for rapid roll-to-roll manufacturing.

MIT team finds ‘twisted’ graphene getting weirder at ‘magical angle’

Researchers at the Massachusetts Institute of Technology (MIT) have previously found a particularly strange pattern in the “twisted” graphene structure, and now they’ve studied it more closely and found that the more layers it has, the better it will work.

Graphene is a 2D carbon nanomaterial consisting of a hexagonal hexagonal grid of a hexagonal structure of carbon atoms with a sp2 hybrid orbit. This makes them functionally two-dimensional, because the electrons that move through them can only move forward/backward and sideways, not above and below. This makes graphene very conductive.

MIT researchers use graphene and boron nitride to convert terahertz waves to usable energy

Researchers at MIT are working to develop a graphene-based device that may be able to convert ambient terahertz waves into a direct current. The MIT team explains that any device that sends out a Wi-Fi signal also emits terahertz waves —electromagnetic waves with a frequency somewhere between microwaves and infrared light. These high-frequency radiation waves, known as “T-rays,” are also produced by almost anything that registers a temperature, including our own bodies and the inanimate objects around us.

Graphene and boron nitride to help use terahertz energy image

Terahertz waves are pervasive in our daily lives, and if harnessed, their concentrated power could potentially serve as an alternate energy source. Imagine, for instance, a cellphone add-on that passively soaks up ambient T-rays and uses their energy to charge your phone. However, to date, terahertz waves are wasted energy, as there has been no practical way to capture and convert them into any usable form. This is exactly what the MIT scientists set out to do.

Stanford team finds novel form of magnetism in twisted bi-layer graphene

Stanford physicists recently observed a novel form of magnetism, predicted but never seen before, that is generated when two graphene sheets are carefully stacked and rotated to a special angle. The researchers suggest the magnetism, called orbital ferromagnetism, could prove useful for certain applications, such as quantum computing.

bi-layer graphene between hBN gives off orbital ferromagnetism imageOptical micrograph of the assembled stacked structure, which consists of two graphene sheets sandwiched between two protective layers made of hexagonal boron nitride. (Image: Aaron Sharpe)

“We were not aiming for magnetism. We found what may be the most exciting thing in my career to date through partially targeted and partially accidental exploration,” said study leader David Goldhaber-Gordon, a professor of physics at Stanford’s School of Humanities and Sciences. “Our discovery shows that the most interesting things turn out to be surprises sometimes.”

MIT team uses wax to smooth out wrinkles in graphene

Researchers at MIT have utilized an everyday material - wax- to protect graphene from performance-impairing wrinkles and contaminants. Removing graphene from the substrate it’s grown on and transferring it to a new substrate is known t be challenging. Traditional methods encase the graphene in a polymer that protects against breakage but also introduces defects and particles onto graphene’s surface. These interrupt electrical flow and stifle performance.

MIT process for smoothing out graphene wrinkles with wax imagea Schematics showing the process of paraffin-assisted graphene transfer. b Schematics showing the effect of paraffin’s thermal expansion on graphene wrinkle. c A typical paraffin-supported graphene film floated on water at different temperatures

The MIT team describes a fabrication technique that applies a wax coating to a graphene sheet and heats it up. Heat causes the wax to expand, which smooths out the graphene to reduce wrinkles. Moreover, the coating can be washed away without leaving behind much residue.