Research ArticleMATERIALS SCIENCE

A nanofluidic ion regulation membrane with aligned cellulose nanofibers

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Science Advances  22 Feb 2019:
Vol. 5, no. 2, eaau4238
DOI: 10.1126/sciadv.aau4238
  • Fig. 1 Ion transport within the aligned cellulose nanofibers.

    (A) A tree trunk containing cellulose nanofibers. (B) Schematic of the removal of intertwined lignin and hemicellulose from natural wood to make the nanofluidic membrane. (C) A nanofluidic membrane that inherits the nanofiber alignment direction from natural wood, as marked. (D) Schematic of the low tortuosity nanofluidic membrane. Photo Credit: T.L., University of Maryland, College Park. Permission granted.

  • Fig. 2 Characterizations of the delignified wood.

    Photos of various configurations of the (A) nanofluidic cellulose membrane, including (B) a cellulose cable wrapped around a rod. The arrows indicate the nanofiber alignment direction. Scale bars, 1 cm. (C) Side view SEM image of the cellulose membrane and (D) the aligned cellulose nanofibers at higher magnification. (E) Top view SEM image showing the tips of the cellulose nanofibers. (F) The elliptical shape of the diffraction pattern in SAXS for the dry and wet membrane, indicating the molecular level alignment of cellulose. (G) The transmittance of the dry and wet cellulose membrane.

  • Fig. 3 Ionic conductivity measurement with chemical modifications and physical densifications.

    (A) Ionic conductivity measurement setup. (B) Zeta potential of the cellulose fibers and oxidized/surface-charged cellulose under neutral pH with a concentration of cellulose approximately 0.1%. (C) An ionic conductivity test with KCl solution for the cellulose membrane before and after oxidization. The oxidized cellulose exhibits an increased ionic conductivity plateau due to the higher surface charge. (D) Ionic conductivity of the undensified cellulose and densified cellulose membrane in KCl solution.

  • Fig. 4 A cellulose-based ionic transistor.

    (A) Schematic of a freestanding cellulose nanofluidic transistor with a painted metal contact for gating. (B) Schematic of the gating effect on the ion distribution within the cellulose membrane. (C) Current-voltage characteristics of the cellulose nanofiber membrane with different gating voltages from −2 to 2 V. (D) Characterization of the transistor using varied gating voltages. Inset: Semi-log plot of ionic current versus gating voltage. (E) Photo image of a flexible and biocompatible cellulose nanofiber ribbon. (F) Ion conductivity shows minimal change upon folding.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/2/eaau4238/DC1

    Fig. S1. Highly hydrophilic cellulose demonstrating directional fluidic transport.

    Fig. S2. Composition results of the natural wood and the wood membrane after step I and II treatments.

    Fig. S3. The mechanical tensile strength for the densified and undensified samples.

    Fig. S4. Current-voltage characteristics of the membrane infiltrated multiple times with 10−5 M KCl solution.

    Fig. S5. Tensile strength of the membranes that underwent different dry-wet cycles.

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Highly hydrophilic cellulose demonstrating directional fluidic transport.
    • Fig. S2. Composition results of the natural wood and the wood membrane after step I and II treatments.
    • Fig. S3. The mechanical tensile strength for the densified and undensified samples.
    • Fig. S4. Current-voltage characteristics of the membrane infiltrated multiple times with 10−5 M KCl solution.
    • Fig. S5. Tensile strength of the membranes that underwent different dry-wet cycles.

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