Research ArticleMATERIALS SCIENCE

MXenes stretch hydrogel sensor performance to new limits

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Science Advances  15 Jun 2018:
Vol. 4, no. 6, eaat0098
DOI: 10.1126/sciadv.aat0098
  • Fig. 1 Characterizations of M-hydrogel.

    (A) Transmission electron microscopy (TEM) of MXene nanosheets; shown in the upper right is the HRTEM image of a typical nanosheet, and shown in the lower right is the corresponding fast Fourier transform (FFT). (B) Photographs demonstrating the stretchability of M-hydrogel. (C) Photographs depicting the self-healing capability of the M-hydrogel: two cut pieces (top), once gently touched (middle), and showing retention of the original stretchability of M-hydrogel (bottom). (D) TEM image of M-hydrogel. (E) 3D tomography image based on the entire area in (D) and (F) zoomed-in 3D tomography image of a selected volume marked with red box in (E).

  • Fig. 2 Electromechanical properties of M-hydrogel composite and mechanisms.

    (A to F) Electrical response of M-hydrogel to (A) tensile strain and (B) compressive strain, with insets showing the corresponding GFs; scanning electron microscopy (SEM) images of M-hydrogel surface (C) before and (D) after stretching; and (E and F) a schematic illustration of the mechanism of the electromechanical responses of M-hydrogel. wt %, weight %.

  • Fig. 3 Sensing capability of M-hydrogel to motions on its surface.

    Resistance change of M-hydrogel in response to motion on its surface (A) vertical to the current direction and (B) parallel to the current direction. (C) Experimental setup to explain the motion direction sensing capability of M-hydrogel and corresponding result. (D) Schematic for motion speed sensing. (E) Speed sensing result comparison between M-hydrogel and pristine hydrogel. (F) Motion sensing of M-hydrogel in response to different motion speeds.

  • Fig. 4 General sensing performance of M-hydrogel.

    (A to E) Resistance change of M-hydrogel in response to (A) finger bending, (B) different hand gestures, (C) human pulse, and (D and E) facial expressions.

  • Fig. 5 Advanced sensing applications of M-hydrogel.

    (A) Schematic for signature sensing. (B to D) Resistance change to (B) signature and (C and D) OK written by different volunteers. (E) Schematic for vocal sensing. (F to H) Resistance change in response to similarly sounding letters “B,” “D,” and “E.”

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/6/eaat0098/DC1

    fig. S1. Characterization of MXene (Ti3C2Tx) nanosheets.

    fig. S2. Tensile fracture behaviors of pristine hydrogel.

    fig. S3. Schematics of the uniformly dispersed polymer-clay network structure of M-hydrogel.

    fig. S4. Experimental setup for electromechanical responses of M-hydrogel under compression.

    fig. S5. Electromechanical response of M-hydrogel to vertical motion of object on its surface.

    fig. S6. Anisotropic electric response of M-hydrogel to tensile and compressive strain.

    fig. S7. Motion direction sensing comparison between the pristine hydrogel and M-hydrogel.

    fig. S8. Mechanism of the speed-sensitive property of M-hydrogel.

    fig. S9. Handwriting and vocal sensing performances of pristine hydrogel.

    table S1. GF comparison between the M-hydrogel (4.1 wt %)–based sensor and recently reported hydrogel-based sensors.

    movie S1. Stretchability and self-healability of M-hydrogel.

    movie S2. Stretchability and self-healability of pristine hydrogel.

    movie S3. Tensile fracture demonstration of M-hydrogel.

    movie S4. Tensile fracture demonstration of pristine hydrogel.

    movie S5. In situ TEM observation with varying tilt angle.

    movie S6. In situ TEM observation with varying depth of focus.

    References (36, 37)

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Characterization of MXene (Ti3C2Tx) nanosheets.
    • fig. S2. Tensile fracture behaviors of pristine hydrogel.
    • fig. S3. Schematics of the uniformly dispersed polymer-clay network structure of M-hydrogel.
    • fig. S4. Experimental setup for electromechanical responses of M-hydrogel under compression.
    • fig. S5. Electromechanical response of M-hydrogel to vertical motion of object on its surface.
    • fig. S6. Anisotropic electric response of M-hydrogel to tensile and compressive strain.
    • fig. S7. Motion direction sensing comparison between the pristine hydrogel and M-hydrogel.
    • fig. S8. Mechanism of the speed-sensitive property of M-hydrogel.
    • fig. S9. Handwriting and vocal sensing performances of pristine hydrogel.
    • table S1. GF comparison between the M-hydrogel (4.1 wt %)–based sensor and recently reported hydrogel-based sensors.
    • References (36, 37)

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    Other Supplementary Material for this manuscript includes the following:

    • movie S1 (.avi format). Stretchability and self-healability of M-hydrogel.
    • movie S2 (.avi format). Stretchability and self-healability of pristine hydrogel.
    • movie S3 (.avi format). Tensile fracture demonstration of M-hydrogel.
    • movie S4 (.avi format). Tensile fracture demonstration of pristine hydrogel.
    • movie S5 (.avi format). In situ TEM observation with varying tilt angle.
    • movie S6 (.avi format). In situ TEM observation with varying depth of focus.

    Files in this Data Supplement:

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