The researchers made their slit devices from two 100-nm thick crystal slabs of graphite measuring several microns across that they obtained by shaving off bulk graphite crystals. They then placed rectangular-shaped pieces of 2D atomic crystals of bilayer graphene and monolayer MoS2 at each edge of one of the graphite crystal slabs before placing another slab on top of the first. This produces a gap between the slabs that has a height equal to the spacers’ thickness.
“It’s like taking a book, placing two matchsticks on each of its edges and then putting another book on top.” explains Geim. “This creates a gap between the books’ surfaces with the height of the gap being equal to the matches’ thickness. In our case, the books are the atomically flat graphite crystals and the matchsticks are the graphene, or MoS2 monolayers.”
The assembly is held together by van der Waals forces and the slits are roughly the same size as the diameter of aquaporins, which are vital for living organisms. The slits are the smallest size possible since slits with thinner spacers are unstable and collapse because of attraction between opposite walls.
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Published by Manchester 1824