Research ArticleAPPLIED SCIENCES AND ENGINEERING

Robust nanogenerators based on graft copolymers via control of dielectrics for remarkable output power enhancement

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Science Advances  26 May 2017:
Vol. 3, no. 5, e1602902
DOI: 10.1126/sciadv.1602902
  • Fig. 1 Synthesis of PVDF-Gn graft copolymers.

    (A) Synthesis of PVDF-Gn graft copolymers and photograph of the PVDF and PVDF-G18 NMP solutions. 1H NMR (B) and FTIR (C) of PVDF and PVDF-Gn.

  • Fig. 2 Fabrication of PVDF-Gn–based TENGs and its output performance.

    (A) Schematic diagrams of the fabrication process for the PVDF-Gn–based TENGs. (B) Photographs of a flexible PVDF-Gn film after it was peeled off and a PVDF-Gn–based TENG. (C) Output current densities generated by the PVDF-based TENGs as a function of the PtBA mole percent ranging from 0 to 18%. (D) Output voltages, current densities, and output power densities of the PVDF-G18–based TENG with the resistance of external loads from 1 to 109 ohms. (E) Charge densities generated by the PVDF-based TENGs as a function of the PtBA mole percent ranging from 0 to 18%. (F) Measured voltage of a commercial capacitor (1, 2.2, 3.3, 10, 22, 33, 100, 220, 330, and 1000 μF) charged with ac-to-dc signal converting circuit using PVDF-G18–based TENG.

  • Fig. 3 Mechanical bending, stability, and durability test of PVDF-Gn–based TENG.

    (A) Mechanical bending tests of the PVDF-based TENG. (B) Output current densities generated by pristine PVDF– and PVDF-G18–based TENGs before and after bending 3000 times. (C) Stability and durability test of the TENG under cycled compressive force of 50 N over 18,000 cycles.

  • Fig. 4 Dielectric constant and loss tangent for PVDF-Gn films.

    Frequency dependence of (A) dielectric constant values and (B) loss tangent for PVDF-based films with various PtBA mole percents ranging from 0 to 18%.

  • Fig. 5 Relationship between the dielectric constant and output performance of PVDF-Gn–based TENG.

    (A) Measured output currents of the PVDF-based TENG with the grafting ratio. (B) Saturated time and output current as a function of the PtBA mole percent ranging from 0 to 18%. Error bars represent SEM. (C) Calculated charging time of the capacitor increases from 2.3 to 4.52 s with the increase of the dielectric constant.

  • Fig. 6 Surface potential and UPS measurement of PVDF-Gn films.

    (A) KPFM surface potential distribution images (3 μm × 3 μm) of Au, pristine PVDF, and PVDF-G18 films. (B) Work function values of pristine PVDF and PVDF-G18 films, obtained from the KPFM results. (C) UPS spectra and (D) the change in work function of Al, pristine PVDF, and PVDF-G18 films. Error bars represent SEM.

  • Fig. 7 XRD pattern of PVDF-Gn films.

    (A) High-resolution XRD patterns of pristine PVDF and PVDF-Gn films as a function of PtBA mole percent. (B) Expanded view of the second peak in (A). The peak can be deconvoluted into two peaks, α (110) (red) and β (200) (blue) phases.

  • Fig. 8 Output performance depending on the poling electric field direction.

    Output voltages and current densities for (A) pristine PVDF–based and (B) PVDF-G18–based TENGs under different poling electric field directions. (C) Circuit diagrams and different performances among TENGs fabricated under different poling electric field directions.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/3/5/e1602902/DC1

    fig. S1. Output voltages of PVDF-based TENGs.

    fig. S2. Output performances of different polymer-based TENGs.

    fig. S3. Output performance of pristine PVDF–based TENG with the resistance of external loads.

    fig. S4. Average current density and charge density.

    fig. S5. Calculated electrostatic potentials.

    fig. S6. Capacitor charging properties of pristine PVDF–based TENGs.

    fig. S7. AFM and SEM images of the PVDF-Gn films.

    fig. S8. Nanoindentation test for the PVDF-Gn films.

    fig. S9. Dielectric constant of PVDF-Gn films according to PtBA mole percents.

    fig. S10. Structures of PVDF and PVDF-Gn.

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Output voltages of PVDF-based TENGs.
    • fig. S2. Output performances of different polymer-based TENGs.
    • fig. S3. Output performance of pristine PVDF–based TENG with the resistance of external loads.
    • fig. S4. Average current density and charge density.
    • fig. S5. Calculated electrostatic potentials.
    • fig. S6. Capacitor charging properties of pristine PVDF–based TENGs.
    • fig. S7. AFM and SEM images of the PVDF-Gn films.
    • fig. S8. Nanoindentation test for the PVDF-Gn films.
    • fig. S9. Dielectric constant of PVDF-Gn films according to PtBA mole percents.
    • fig. S10. Structures of PVDF and PVDF-Gn.

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