Carbon Nanotubes as Thermally Induced Water Pumps

Elton Oyarzua, Jens Honore Walther, Constantine M Megaridis, Petros Koumoutsakos, Harvey A Zambrano

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    Abstract

    Thermal Brownian motors (TBMs) are nanoscale machines that exploit thermal fluctuations to provide useful work. We introduce a TBM-based nanopump which enables continuous water flow through a carbon nanotube (CNT) by imposing an axial thermal gradient along its surface. We impose spatial asymmetry along the CNT by immobilizing certain points on its surface. We study the performance of this molecular motor using molecular dynamics (MD) simulations. From the MD trajectories, we compute the net water flow and the induced velocity profiles for various imposed thermal gradients. We find that spatial asymmetry modifies the vibrational modes of the CNT induced by the thermal gradient, resulting in a net water flow against the thermal gradient. Moreover, the kinetic energy associated with the thermal oscillations rectifies the Brownian motion of the water molecules, driving the flow in a preferred direction. For imposed thermal gradients of 0.5-3.3 K/nm, we observe continuous net flow with average velocities up to 5 m/s inside CNTs with diameters of 0.94, 1.4, and 2.0 nm. The results indicate that the CNT-based asymmetric thermal motor can provide a controllable and robust system for delivery of continuous water flow with potential applications in integrated nanofluidic devices.
    Original languageEnglish
    JournalA C S Nano
    Volume11
    Issue number10
    Pages (from-to)9997–10002
    ISSN1936-0851
    DOIs
    Publication statusPublished - 2017

    Keywords

    • Molecular dynamics
    • Nanofluidics
    • Single-walled carbon nanotubes
    • Thermal pump
    • Thermal vibrations

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