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Electric-field-induced wetting and dewetting in single hydrophobic nanopores


The behaviour of water in nanopores is very different from that of bulk water1,2. Close to hydrophobic surfaces, the water density has been found to be lower than in the bulk3, and if confined in a sufficiently narrow hydrophobic nanopore, water can spontaneously evaporate1,4. Molecular dynamics simulations have suggested that a nanopore can be switched between dry and wet states by applying an electric potential across the nanopore membrane5,6,7,8. Nanopores with hydrophobic walls could therefore create a gate system for water, and also for ionic and neutral species. Here, we show that single hydrophobic nanopores can undergo reversible wetting and dewetting due to condensation and evaporation of water inside the pores. The reversible process is observed as fluctuations between conducting and non-conducting ionic states and can be regulated by a transmembrane electric potential.

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Figure 1: Hydrophobic gating in a 16-nm-diameter conically shaped nanopore modified in 12 mM (trimethylsilyl)diazomethane for 15 min.
Figure 2: Reversibility of the opening and closing of a hydrophobic nanopore with voltage.
Figure 3: Hydrophobic gating studied in a degassed solution of 1 M KCl.
Figure 4: Scheme of hydrophobic gating with an electric field.

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Irradiation with swift heavy ions was performed at the Gesellschaft fuer Schwerionenforschung (GSI, Darmstadt, Germany). This research was supported by the National Science Foundation (CHE 0747237). Z.S.S. was supported as part of the Nanostructures for Electrical Energy Storage, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences (award no. DESC0001160). The authors acknowledge discussions with C. Martens.

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Z.S.S., M.D. and K.J.S. conceived the experiments. M.R.P., L.C. and M.D. performed the experiments. All authors contributed to writing the manuscript. M.R.P., L.C., M.D., K.J.S. and Z.S.S. discussed the results and explained the transient behaviour of ion current in hydrophobic pores.

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Correspondence to Zuzanna S. Siwy.

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Powell, M., Cleary, L., Davenport, M. et al. Electric-field-induced wetting and dewetting in single hydrophobic nanopores. Nature Nanotech 6, 798–802 (2011).

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