Research ArticleAPPLIED SCIENCES AND ENGINEERING

All-printed magnetically self-healing electrochemical devices

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Science Advances  02 Nov 2016:
Vol. 2, no. 11, e1601465
DOI: 10.1126/sciadv.1601465
  • Fig. 1 Schematic showing self-healing principle and fabrication process.

    (A) Image of a self-healing circuit demonstrating its autonomous recovery upon complete damage (damage width, 3 mm). The scheme at the top shows the working principle of the self-healing process. The printed self-healing trace consists of aligned NMPs, which produce a net magnetic field along the length of the trace, thus making the trace behave as a bar magnet (left image + scheme). When the trace is severed, the two pieces behave as individual bar magnets, with opposite poles attracting each other (middle image + scheme). The strong magnetic attraction between the two severed pieces forces them to move toward each other to regain the mechanical and electrical connectivity (right image + scheme). (B) Pictorial representation of the printing process for realizing the self-healing trace. The scheme illustrates the initial random orientation of the NMPs within the printed trace and gradual alignment.

  • Fig. 2 XRD, SEM-EDX, and three-dimensional optical characterization.

    (A) XRD spectra for NMPs. (B) Magnetic hysteresis curves for NMPs (black plot) and self-healing trace (red plot). SEM (C), EDX (for neodymium) (C′), and EDX (for carbon) (C″) images of an aligned self-healing printed trace. SEM (D), EDX (for neodymium) (D′), and EDX (for carbon) (D″) images of a nonaligned printed trace. (E) SEM image of a printed trace based on a CB ink (no NMPs). Three-dimensional (3D) optical images of (F) aligned and (G) nonaligned printed traces. Scale bars, 200 μm (C to E). Scale bars in μm (F and G). emu, electromagnetic unit; cps, counts per second; kOe, kilo-oersted.

  • Fig. 3 Electrical conductivity studies for studying self-healing process.

    Electrical conductivity–based studies to analyze the self-healing ability of a self-healing printed trace (A) when repeatedly damaged at the same location (damage widths, 1 to 3 mm) and (B) when damaged at multiple locations (damage width, 1 mm). Inset for the respective panels shows zoomed-in plots, illustrating the conductivity recovery of the self-healing traces upon damage. The dotted red line represents the time when the self-healing process is allowed to take place. Electrical conductivity studies revealing the inability of a printed trace consisting of (C) nonaligned NMPs and (D) only CB (no NMPs) to recover electrical connectivity when completely damaged.

  • Fig. 4 Electrochemical characterization of self-healing electrodes.

    CV plots for printed self-healing traces (A) with varying amounts of NMPs and (B) at different scan rates. (C) Plot showing linear dependence of anodic (black plot) and cathodic (red plot) peak current versus square root of scan rate. (D) Nyquist plot for self-healing printed electrode (inset: schematic showing the electrical circuit simulating the electrode-electrolyte interface). (E) CV plots recorded for a self-healing trace before any damage (black plot), after first damage with a width of 1 mm (red plot), and after nine repeated damages (blue plot) at the same location (three times each for damage widths of 1, 2, and 3 mm). (F) CV plot illustrating real-time recovery of three repeated 3-mm-wide damages. Individual CVs showing the point at which the electrode is damaged and the point where the self-healing is initiated for the (G) first, (H) second, and (I) third consecutive 3-mm-wide damage at the same location (“ci” to “ciii” represent the time when the electrode was damaged by 3 mm three times, whereas “hi” to “hiii” represent the time when the healing process began after the corresponding damage). (G to I) Green, black, and red colors represent data before cutting, during damage, and after healing, respectively.

  • Fig. 5 Self-healing batteries and electrochemical sensors.

    (A) Recovery of the current output for a self-healing Zn-Ag2O battery after every 3-mm-wide damage. (B) Photographs showing the self-healing battery at different steps of the damage-heal cycle. (C) Inability of a control (nonhealing CB ink–based) Zn-Ag2O battery to recover current output after the first damage. (D) Photographs showing the control battery at different steps of the damage-heal cycle. Amperometric and voltammetric response of self-healing (E) H2O2 and (F) Cu sensors, respectively, for increasing concentrations of H2O2 (0 to 20 mM) and Cu [0 to 25 parts per million (ppm)] under repeated 1-mm-wide damage.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/2/11/e1601465/DC1

    fig. S1. Real-time CV studies for characterizing the self-healing process.

    movie S1. A magnetically self-healing printed LED circuit immediately recovering repeated macroscopic damages.

    movie S2. Printing process and magnetic orientation of the NMPs dispersed within the printed film required for realizing magnetically self-healing films.

    movie S3. Lifting of the self-healed printed trace against gravity to demonstrate the strength of the self-healing process.

    movie S4. Self-healing of a printed trace after repeated macroscopic damages.

    movie S5. Inability of a printed trace, comprising nonaligned NMPs fabricated in the absence of external magnetic field, to self-heal incurred damage.

    movie S6. Inability of a CB ink (no NMPs)–based printed trace to self-heal incurred damage.

    movie S7. Self-healing printed Zn-Ag2O battery recovering immediately after experiencing repeated macroscopic damages.

    movie S8. Inability of a printed Zn-Ag2O battery, fabricated using CB ink (no NMPs), to recover macroscopic damages.

    movie S9. Damage and autonomous recovery demonstrated by a self-healing wearable LED circuit.

    movie S10. Self-healing of a wearable LED circuit under repeated damage.

    movie S11. Inability of a wearable LED circuit fabricated using CB ink (no NMPs) to recover electrical connectivity after being damaged.

  • Supplementary Materials

    This PDF file includes:

    • fig. S1. Real-time CV studies for characterizing the self-healing process.
    • Legends for movies S1 to S11

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    Other Supplementary Material for this manuscript includes the following:

    • movie S1 (.wmv format). A magnetically self-healing printed LED circuit immediately recovering repeated macroscopic damages.
    • movie S2 (.wmv format). Printing process and magnetic orientation of the NMPs dispersed within the printed film required for realizing magnetically self-healing films.
    • movie S3 (.wmv format). Lifting of the self-healed printed trace against gravity to demonstrate the strength of the self-healing process.
    • movie S4 (.wmv format). Self-healing of a printed trace after repeated macroscopic damages.
    • movie S5 (.wmv format). Inability of a printed trace, comprising nonaligned NMPs fabricated in the absence of external magnetic field, to self-heal incurred damage.
    • movie S6 (.wmv format). Inability of a CB ink (no NMPs)–based printed trace to self-heal incurred damage.
    • movie S7 (.wmv format). Self-healing printed Zn-Ag2O battery recovering immediately after experiencing repeated macroscopic damages.
    • movie S8 (.wmv format). Inability of a printed Zn-Ag2O battery, fabricated using CB ink (no NMPs), to recover macroscopic damages.
    • movie S9 (.wmv format). Damage and autonomous recovery demonstrated by a self-healing wearable LED circuit.
    • movie S10 (.wmv format). Self-healing of a wearable LED circuit under repeated damage.
    • movie S11 (.wmv format). Inability of a wearable LED circuit fabricated using CB ink (no NMPs) to recover electrical connectivity after being damaged.

    Files in this Data Supplement: