Recent adhesive tape picks up and sticks down 2D materials as easily as child’s play

Now, a research team from Kyushu University, in collaboration with Japanese company Nitto Denko, have developed a tape that might be used to stay 2D materials to many various surfaces, in a straightforward and user-friendly way. Their findings were published in Nature Electronics on February 9, 2024.

“Transferring 2D materials is often a really technical and sophisticated process; the fabric can easily tear, or change into contaminated, which significantly degrades its unique properties,” says lead creator, Professor Hiroki Ago of Kyushu University’s Global Innovation Center. “Our tape offers a fast and straightforward alternative, and reduces damage.”

The researchers began by specializing in graphene. Made out of a skinny sheet of carbon atoms, graphene is hard, flexible, and light-weight, with high thermal and electrical conductivity. Dubbed a “wonder material” upon discovery, it has potential applications in biosensing, anti-cancer drug delivery, aeronautics and electronic devices.

“One in every of the foremost methods of creating graphene is thru chemical vapor deposition, where graphene is grown on copper film. But to perform properly, the graphene have to be separated from the copper and transferred onto an insulating substrate, like silicon,” Professor Ago explains. “To do that, a protective polymer is placed over the graphene, and the copper is then removed using etching solution, comparable to acid. Once attached to the brand new substrate, the protective polymer layer is then dissolved with a solvent. This process is expensive, time-consuming and could cause defects to the graphene’s surface or leave traces of the polymer behind.”

Professor Ago and his colleagues subsequently aimed to supply another way of transferring graphene. They used AI to develop a specialized polymer tape, dubbed “UV tape,” which changes its attraction to graphene when irradiated with UV light.

Before exposure to UV light, the tape has a robust adhesion to graphene, allowing it to “stick.” But after UV exposure, the atom bonding changes, which decreases the extent of adhesion to graphene by about 10%. The UV tape also becomes barely stiffer and easier to peel off. Taken together, these changes allow the tape to be peeled off the device substrate while leaving the graphene behind.

The researchers also developed tapes that may transfer two other 2D materials: white graphene (hBN), an insulator that may act as a protective layer when stacking 2D materials, and transition metal dichalcogenides (TMDs), a promising material for the subsequent generation of semiconductors.

Importantly, when the researchers looked closely on the surface of the 2D materials after transfer, they saw a smoother surface with fewer defects than when transferred using the present conventional technique. Upon testing the materials’ properties, additionally they found that they were more efficient.

Transfer using UV tape also offers quite a few other benefits over current transfer techniques. Since the UV tape is bendy, and the transfer process doesn’t require using plastic-dissolving solvents, flexible plastics might be used because the substrate of the device, expanding potential applications.

“For instance, we made a plastic device that uses graphene as a terahertz sensor. Like X-rays, terahertz radiation can go through objects that light cannot, but doesn’t damage the body,” Professor Ago says. “It’s extremely promising for medical imaging or airport security.”

What’s more, the UV tape might be cut to size in order that only the precise amount of 2D material needed is transferred, minimizing waste and reducing cost. 2D layers of various materials may also be easily laid on top of one another in numerous orientations, allowing researchers to explore latest emerging properties from the stacked materials.

For his or her next steps, the researchers are aiming to expand the scale of the UV tape to the dimensions needed for manufacturers. Currently, the most important wafer of graphene that might be transferred is 10 cm in diameter. Professor Ago and his colleagues are also attempting to resolve the issue of wrinkles and bubbles that form on tape, causing small defects.

The research team also hope to enhance stability, in order that 2D materials might be attached to UV tapes for an extended time frame, and distributed to finish users, comparable to other scientists.

“The tip users can then transfer the fabric onto their desired substrate by applying and removing the UV tape like a baby’s sticker, with no training needed,” says Professor Ago. “Such a straightforward method could fundamentally change the form of research and speed up the industrial development of 2D materials.”