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A Landau–Squire Nanojet

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posted on 13.11.2013, 00:00 by Nadanai Laohakunakorn, Benjamin Gollnick, Fernando Moreno-Herrero, Dirk G. A. L. Aarts, Roel P. A. Dullens, Sandip Ghosal, Ulrich F. Keyser
Fluid jets are found in nature at all length scales from microscopic to cosmological. Here we report on an electroosmotically driven jet from a single glass nanopore about 75 nm in radius with a maximum flow rate ∼15 pL/s. A novel anemometry technique allows us to map out the vorticity and velocity fields that show excellent agreement with the classical Landau–Squire solution of the Navier–Stokes equations for a point jet. We observe a phenomenon that we call flow rectification: an asymmetry in the flow rate with respect to voltage reversal. Such a nanojet could potentially find applications in micromanipulation, nanopatterning, and as a diode in microfluidic circuits.