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arXiv · 1910.11206

Molecular streaming and its voltage control in {\aa}ngstr\"om scale channels

Timothée Mouterde·Ashok Keerthi·Anthony. R. Poggioli·Sidra A. Dar·Alessandro Siria·Andre K. Geim·Lydéric Bocquet·Boya Radha
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Abstract

The field of nanofluidics has shown considerable progress over the past decade thanks to key instrumental advances, leading to the discovery of a number of exotic transport phenomena for fluids and ions under extreme confinement. Recently, van der Waals assembly of 2D materials allowed fabrication of artificial channels with angstr\"om-scale precision. This ultimate confinement to the true molecular scale revealed unforeseen behaviour for both mass and ionic transport. In this work, we explore pressure-driven streaming in such molecular-size slits and report a new electro-hydrodynamic effect under coupled pressure and electric force. It takes the form of a transistor-like response of the pressure induced ionic streaming: an applied bias of a fraction of a volt results in an enhancement of the streaming mobility by up to 20 times. The gating effect is observed with both graphite and boron nitride channels but exhibits marked material-dependent features. Our observations are rationalized by a theoretical framework for the flow dynamics, including the frictional interaction of water, ions and the confining surfaces as a key ingredient. The material dependence of the voltage modulation can be traced back to a contrasting molecular friction on graphene and boron nitride. The highly nonlinear transport under molecular-scale confinement offers new routes to actively control molecular and ion transport and design elementary building blocks for artificial ionic machinery, such as ion pumps. Furthermore, it provides a versatile platform to explore electro-mechanical couplings potentially at play in recently discovered mechanosensitive ionic channels.

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Timothée Mouterde, Ashok Keerthi, Anthony. R. Poggioli, Sidra A. Dar, Alessandro Siria, Andre K. Geim, Lydéric Bocquet, Boya Radha. 2019-10-24. Molecular streaming and its voltage control in {\aa}ngstr\"om scale channels. https://doi.org/10.1038/s41586-019-0961-5

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