Let’s say you’re an engineer with an idea for a new car. But before you can even start experimenting, you have to spend hours casting screws and making rubber for tires from scratch.
This is similar to the challenge faced by researchers trying to invent new types of technology. The ability to manufacture, for example, a flexible screen or a new solar panel, begins with the discovery of a new combination of materials with unusual properties at the atomic scale. But in the field of 2D materials, which is considered one of the most exciting areas for the electronics of the future, scientists still have to painstakingly handcraft each potential new material before they can test its capabilities.
A new technique requires a robot to lend a hand. Developed by scientists from the University of Chicago, Cornell University and the University of Michigan, the research presents an innovative manufacturing method for assembling nanomaterials.
Scientists hope the process, published Jan. 24 in Nature’s nanotechnologycould accelerate the pace of breakthroughs in the field.
“This process is fully automated – you can schedule it and go,” said co-first author Andrew Mannix, a former Kadanoff-Rice postdoctoral fellow at the University of Chicago who is now an assistant professor at Stanford University. “Before, if you wanted to try 10 different permutations of materials, it was all done by hand, which took weeks of work. We can now do it in an hour. We hope this opens up new avenues of research in this exciting field by reducing the drudgery of the work.
A tiny assembly line
The field of 2D materials consists of stacking sheets of a few atoms in thickness each. When the layers are this thin, even ordinary materials often produce surprising new behaviors. For example, carbon suddenly displays superconductivity, the ability to conduct electricity flawlessly, when two layers are stacked vertically at a “magical” angle.
Scientists are particularly interested in stacking different types of 2D materials, Mannix said: “It’s been realized recently that if you can take these layers and stack them by controlling the orientation of the crystal, you can get a Truly beautiful new physics as the interactions between layers are changed.
However, the discovery process is limited and slow, as scientists must first painstakingly assemble these combinations and test them one by one.
UChicago scientists set out to solve this problem. Led by Professor Jiwoong Park, a nanomaterials expert, the group had already invented a way to make complex sheets atomically thin, peel them off and stack them. Now they needed a way to automate this process.
They wanted to create a kind of small assembly line, but each element of the manufacturing process presented its own challenges. First, the scientists had to find a way to precisely cut their leaves into the exact shapes they wanted, which is difficult to do cleanly without breaking or damaging the leaves. “Through experimentation, we have found a technique that can achieve a pattern over a large area with very high precision and without contaminating the material,” said Andrew Ye, Ph.D. student in Park’s lab and the other co-first author of the paper.
The next challenge was to make a robot “hand” capable of maneuvering these extremely fragile sheets. “I needed to find a polymer that was precise enough to grab the leaves,” Mannix said, “but also able to release them again, gently and in the right place.”
They invented a “hand” made of soft polymers that crumble when exposed to heat or ultraviolet light. Once the leaf is precisely positioned, the hand dissolves and the leaf falls into place.
With this system, scientists could now program their assembly line to create a hardware structure with dozens of different layers, walk away, and back to a finished sample ready for testing in minutes.
Not only is the system highly accurate, but it also offers plenty of customization options, including the coveted ability to rotate each successive sheet to different angles.
“When we started looking at this problem, it seemed unimaginable to automate it,” said Park, who is appointed to both the Department of Chemistry and the Pritzker School of Molecular Engineering. “This should dramatically accelerate the pace of discovery. It’s kind of like the difference between handwriting a book letter by letter and using a printing press.
Other study authors included University of Chicago graduate students Fauzia Mujid and Robert Shreiner; postdoctoral researchers Myungjae Lee and Jong-Hoon Kang; Chibeom Park, formerly a postdoctoral researcher and now at the Samsung Electronics Semiconductor Research Center; Teacher. Alex High of the Pritzker School of Molecular Engineering and Argonne National Laboratory; Ariana Ray and Professor David Muller of Cornell; and Suk Hyun Sung and Professor Robert Hovden of the University of Michigan.
The research involved the University of Chicago Materials Science and Technology Research Center, Pritzker Nanofabrication Facility, Searle Cleanroom, Michigan Center for Materials Characterization, and Cornell Center for Materials Research.
Quote: “Robotic four-dimensional pixel assembly of van der Waals solids.” Mannix et al, Nature Nanotechnology, January 24, 2022.
Funding: National Science Foundation, Air Force Office of Scientific Research, Samsung Advanced Institute of Technology, Department of Defense, WM Keck Foundation, Army Research Office.