Ultrafast Propulsion of Water Nanodroplets on Patterned Graphene

Ermioni Papadopoulou, Constantine M. Megaridis, Jens H. Walther, Petros Koumoutsakos*

*Corresponding author for this work

    Research output: Contribution to journalJournal articleResearchpeer-review

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    Abstract

    The directed transport of liquids at the nanoscale is of great importance for nanotechnology applications ranging from water filtration to the cooling of electronics and precision medicine. Here we demonstrate such unidirectional, pumpless transport of water nanodroplets on graphene sheets patterned with hydrophilic/phobic areas inspired by natural systems. We find that spatially varying patterning of the graphene surfaces can lead to water transport at ultrafast velocities, far exceeding macroscale estimates. We perform extensive molecular dynamics simulations to show that such high transport velocities (O(102 m/s)) are due to differences of the advancing and receding contact angles of the moving droplet. This contact angle hysteresis and the ensuing transport depend on the surface pattern and the droplet size. We present a scaling law for the driving capillary and resisting friction forces on the water droplet and use it to predict nanodroplet trajectories on a wedge-patterned graphene sheet. The present results demonstrate that graphene with spatially variable wettability is a potent material for fast and precise transport of nanodroplets with significant potential for directed nanoscale liquid transport and precision drug delivery.
    Original languageEnglish
    JournalACS Nano
    Volume13
    Issue number5
    Pages (from-to)5465-5472
    ISSN1936-0851
    DOIs
    Publication statusPublished - 2019

    Keywords

    • Nanodroplets
    • Graphene
    • Nanofluidics
    • Wettability gradient
    • Wettability patterning

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