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2D layered devices can self-assemble with precision

Wednesday, July 5, 2017
Single-molecule-high sheets of graphene oxide mix in solution with synthetic tandem-repeat proteins patterned on squid ring teeth. The two separate materials self-assemble so that the tandem-repeat protein attach to the edges of the graphene oxide sheets — one end on a sheet — to bring the graphene into stacks and uniformly space the sheets. The amount of spacing between graphene oxide sheets is determined by the length of the tandem repeat protein. Image: Penn State

Squid-inspired proteins can act as programmable assemblers of 2D materials, like graphene oxide, to form hybrid materials with minute spacing between layers suitable for high-efficiency devices including flexible electronics, energy storage systems and mechanical actuators, according to an interdisciplinary team of Penn State researchers.

"2D layered materials can be made by vacuum (chemical vapor) deposition," said Melik C. Demirel, Pierce Development Professor and professor of engineering science and mechanics. "But the process is expensive and takes a long time. With chemical vapor deposition the problem also is we can't scale up."

Materials like graphene oxide are composed of single layers of molecules connected in a plain. While the length and breadth of the sheet can be anything, the height is only that of one molecule. To make usable composites and devices, 2D materials must be stacked either in piles of identical sheets or combinations of sheets of different composition stacked to specification. Together with Mauricio Terrones, professor of physics, chemistry and materials science and engineering, and director of 2D Atomic Center, Penn State, Demirel and his team are currently looking at stacking sheets of identical materials using a solvent approach that self assembles.

"Using the solvent approach the molecules are self-assembling, self-healing and flexible," said Demirel. "Currently we are stacking identical layers, but they don't have to be the same."