Molecular transport through capillaries made with atomic-scale precision.
Nanometre-scale pores and capillaries have long been studied because of their importance in many natural phenomena and their use in numerous applications. A more recent development is the ability to fabricate artificial capillaries with nanometre dimensions, which has enabled new research on molecular transport and led to the emergence of nanofluidics. But surface roughness in particular makes it challenging to produce capillaries with precisely controlled dimensions at this spatial scale. Here we report the fabrication of narrow and smooth capillaries through van der Waals assembly, with atomically flat sheets at the top and bottom separated by spacers made of two-dimensional crystals with a precisely controlled number of layers. We use graphene and its multilayers as archetypal two-dimensional materials to demonstrate this technology, which produces structures that can be viewed as if individual atomic planes had been removed from a bulk crystal to leave behind flat voids of a height chosen with atomic-scale precision. Water transport through the channels, ranging in height from one to several dozen atomic planes, is characterized by unexpectedly fast flow (up to 1 metre per second) that we attribute to high capillary pressures (about 1,000 bar) and large slip lengths. For channels that accommodate only a few layers of water, the flow exhibits a marked enhancement that we associate with an increased structural order in nanoconfined water. Our work opens up an avenue to making capillaries and cavities with sizes tunable to ångström precision, and with permeation properties further controlled through a wide choice of atomically flat materials available for channel walls.
School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
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Radha
School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
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Esfandiar
Chinese Academy of Sciences Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230027, China.
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Wang
School of Materials, University of Manchester, Manchester M13 9PL, UK.
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Rooney
School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
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Gopinadhan
School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
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Keerthi
School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
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Mishchenko
School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
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Janardanan
National Graphene Institute, University of Manchester, Booth Street East, Manchester M13 9PL, UK.
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Blake
School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.|National Graphene Institute, University of Manchester, Booth Street East, Manchester M13 9PL, UK.
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Fumagalli
School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
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Lozada-Hidalgo
Department of Physics, National University of Singapore, 117542 Singapore.
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Garaj
School of Materials, University of Manchester, Manchester M13 9PL, UK.
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Haigh
School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
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Grigorieva
Chinese Academy of Sciences Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui 230027, China.
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Wu
School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
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Geim