Research ArticleAPPLIED SCIENCES AND ENGINEERING

Strong adhesion of wet conducting polymers on diverse substrates

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Science Advances  20 Mar 2020:
Vol. 6, no. 12, eaay5394
DOI: 10.1126/sciadv.aay5394
  • Fig. 1 Strong adhesion of wet conducting polymers on diverse substrates.

    (A) Strong adhesion of a wet conducting polymer on an amine-functionalized substrate with a hydrophilic polymer adhesive layer. (B) Strong adhesion of a conducting polymer on a substrate with an adhesive layer in wet environment. (C) Solvent-casted wet PEDOT:PSS (10 μm thickness) on a polyimide substrate with a PU adhesive layer (60 nm thickness) can withstand mechanical deformations including twisting, bending, and even folding (the radius of curvature ~ 250 μm) without interfacial failure. Photo credit: Hyunwoo Yuk, MIT. (D) Weak and unstable adhesion of a conducting polymer on a substrate without the adhesive layer in wet environment. (E) Solvent-casted wet PEDOT:PSS (10 μm thickness) on a polyimide substrate without the adhesive layer undergoes interfacial failure upon mechanical deformation of the substrate. Photo credit: Hyunwoo Yuk, MIT. (F) Distribution of carbon and sulfur atoms in a PU adhesive interface between an adhered PEDOT:PSS (5 μm thickness) and a PU-coated silicon substrate (1500 nm PU thickness).

  • Fig. 2 Strong adhesion of wet conducting polymers on diverse substrates.

    (A) Image of a lap-shear test setup. Photo credit: Hyunwoo Yuk, MIT. (B) Image of adhesive failure during a lap-shear test of a wet PEDOT:PSS adhered on a pristine glass or a pristine glass with the PU adhesive layer. Photo credit: Hyunwoo Yuk, MIT. (C) Image of cohesive failure during a lap-shear test of a wet PEDOT:PSS adhered on an amine-functionalized glass with the PU adhesive layer. Photo credit: Hyunwoo Yuk, MIT. (D) Lap-shear strengths of wet PEDOT:PSS on a pristine glass substrate without the PU adhesive layer, a pristine glass substrate with the PU adhesive layer, and an amine-functionalized glass substrate with the PU adhesive layer. (E) Lap-shear strengths of various wet conducting polymers (PEDOT:PSS, PPy, and PAni) on pristine glass substrates without the PU adhesive layer and amine-functionalized glass substrates with the PU adhesive layer. (F) Lap-shear strengths of a wet PEDOT:PSS on various amine-functionalized insulating and conductive substrates with the PU adhesive layers. Conducting polymers with 50 μm thickness and PU adhesive layers with 60 nm thickness were used for all experiments. Values in (C) to (E) represent the mean, and the error bars represent 95% CI of the measured values (n = 5). P values are determined by Student’s t test. **P ≤ 0.01; ***P ≤ 0.001.

  • Fig. 3 Electrical properties of adhesive interface by varying PU adhesive layer thickness.

    (A) Schematic illustration of an electrical conductivity measurement setup for a wet PEDOT:PSS with the PU adhesive layer by the standard four-point probe method. (B) Conductivity of wet PEDOT:PSS with varying PU adhesive layer thickness. (C) Schematic illustration of a sheet resistance measurement setup for a wet PEDOT:PSS prepared on ITO-glass electrodes without and with the PU adhesion layer. (D) Sheet resistance ratio Ri/Rii between a wet PEDOT:PSS prepared on a ITO-glass electrode without the PU adhesion layer and a wet PEDOT:PSS prepared on a ITO-glass electrode with varying thickness of the PU adhesion layer. (E) Schematic illustration of an EIS setup for a wet PEDOT:PSS prepared on an ITO-glass electrode with the PU adhesion layer. (F) EIS curves for a bare ITO-glass electrode, a wet PEDOT:PSS (10 μm thickness) on an amine-functionalized ITO-glass electrode with the PU adhesive layer (60 nm thickness), and a wet PEDOT:PSS (10 μm thickness) on an amine-functionalized ITO-glass electrode with the PU adhesive layer (1500 nm thickness). Values in (B) and (D) represent the mean, and the error bars represent 95% CI of the measured values (n = 5). Statistical significance and P values are determined by one-way ANOVA and Tukey’s multiple comparison test. ****P ≤ 0.0001; ns, not significant.

  • Fig. 4 Adhesion stability of solvent-casted wet conducting polymers.

    (A) Images of a solvent-casted wet PEDOT:PSS on a ITO-glass substrate without the PU adhesive layer before and after ultrasonication for 1 min. Photo credit: Hyunwoo Yuk, MIT. (B) Images of a solvent-casted wet PEDOT:PSS on an amine-functionalized ITO-glass substrate with the PU adhesive layer before and after ultrasonication for 10 min. Photo credit: Hyunwoo Yuk, MIT. (C) EIS curves for a solvent-casted wet PEDOT:PSS on amine-functionalized ITO-glass substrates with the PU adhesive layer before and after ultrasonication for 10 min. (D) Long-term CV curves for a solvent-casted wet PEDOT:PSS on an amine-functionalized Pt electrode with the PU adhesive layer in PBS. (E) Measured CSC versus CV cycle number for a solvent-casted wet PEDOT:PSS on an amine-functionalized Pt electrode with the PU adhesive layer in PBS. Photo credit: Hyunwoo Yuk, MIT. Conducting polymers with 10 μm thickness and PU adhesive layers with 60 nm thickness were used for all experiments.

  • Fig. 5 Strong adhesion of wet conducting polymers on various bioelectronic devices.

    (A) Strong adhesion of wet conducting polymers on bioelectronic devices with planar microelectrodes. Images of the devices are reproduced with permission of IOP Publishing Ltd. from (35) (ECoG electrode array) and Wiley-VCH Verlag from (36) (Michigan probe). (B) Strong adhesion of wet conducting polymers on bioelectronic devices with tip-microelectrodes. Images of the devices are reproduced with permission of IEEE from (37) (Utah array) and National Academy of Sciences from (38) (microwire electrode array). (C) EIS curves for electrodeposited wet PEDOT:PSS on amine-functionalized Au electrodes of a commercially available microelectrode array (MEA) with and without the PU adhesive layer before and after ultrasonication in PBS. (D) Optical microscope images of an electrodeposited wet PEDOT:PSS on a MEA without the PU adhesive layer before and after ultrasonication for 5 min in PBS. (E) Optical microscope images of an electrodeposited wet PEDOT:PSS on an amine-functionalized MEA with the PU adhesive layer before and after ultrasonication for 60 min in PBS. (F) EIS curves for electrodeposited wet PEDOT:PSS on amine-functionalized commercially available PTFE-coated Pt microwire electrodes with and without the PU adhesive layer before and after ultrasonication in PBS. (G) SEM images of an electrodeposited PEDOT:PSS on a Pt microwire electrode without the PU adhesive layer before and after ultrasonication for 5 min in PBS. (H) SEM images of an electrodeposited PEDOT:PSS on an amine-functionalized Pt microwire electrode with the PU adhesive layer before and after ultrasonication for 30 min in PBS. Conducting polymers with 500 nm thickness and PU adhesive layers with 60 nm thickness were used for all experiments.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/6/12/eaay5394/DC1

    Fig. S1. Surface roughness of diverse substrates.

    Fig. S2. Amine functionalization of diverse substrates.

    Fig. S3. Strong adhesion of wet conducting polymer by PU adhesive layer.

    Fig. S4. Chemical structures of hydrophilic PU, PEDOT, and PSS.

    Fig. S5. XPS spectra of solvent-casted PEDOT:PSS with varying thickness of PU adhesive layer.

    Fig. S6. Amine functionalization effect on lap-shear strength for diverse substrates.

    Fig. S7. PU adhesive layer thickness effect on lap-shear strength for amine-functionalized glass substrate.

    Fig. S8. Lap-shear test curves for diverse substrates.

    Fig. S9. Adhesion of hydrophilic PU to polyimide.

    Fig. S10. Mechanical properties of wet PEDOT:PSS with varying PU adhesive layer thickness.

    Fig. S11. Nyquist plots for EIS measurements of adhesive interface by varying PU adhesive layer thickness.

    Fig. S12. PU adhesive layer thickness effect on lap-shear strength for amine-functionalized ITO-glass substrates.

    Fig. S13. Adhesion stability of electrodeposited wet conducting polymer.

    Fig. S14. SEM images of electrodeposited PEDOT:PSS on Pt microwire electrode without PU adhesive layer.

    Fig. S15. SEM images of electrodeposited PEDOT:PSS on amine-functionalized Pt microwire electrode with PU adhesive layer.

    Fig. S16. Strong adhesion of wet conducting polymer by PVA adhesive layer.

    Fig. S17. Adhesion of thin spin-coated conducting polymers in wet physiological environment.

    Movie S1. Adhesion stability of wet PEDOT:PSS under cyclic bending deformations.

  • Supplementary Materials

    The PDF file includes:

    • Fig. S1. Surface roughness of diverse substrates.
    • Fig. S2. Amine functionalization of diverse substrates.
    • Fig. S3. Strong adhesion of wet conducting polymer by PU adhesive layer.
    • Fig. S4. Chemical structures of hydrophilic PU, PEDOT, and PSS.
    • Fig. S5. XPS spectra of solvent-casted PEDOT:PSS with varying thickness of PU adhesive layer.
    • Fig. S6. Amine functionalization effect on lap-shear strength for diverse substrates.
    • Fig. S7. PU adhesive layer thickness effect on lap-shear strength for amine-functionalized glass substrate.
    • Fig. S8. Lap-shear test curves for diverse substrates.
    • Fig. S9. Adhesion of hydrophilic PU to polyimide.
    • Fig. S10. Mechanical properties of wet PEDOT:PSS with varying PU adhesive layer thickness.
    • Fig. S11. Nyquist plots for EIS measurements of adhesive interface by varying PU adhesive layer thickness.
    • Fig. S12. PU adhesive layer thickness effect on lap-shear strength for amine-functionalized ITO-glass substrates.
    • Fig. S13. Adhesion stability of electrodeposited wet conducting polymer.
    • Fig. S14. SEM images of electrodeposited PEDOT:PSS on Pt microwire electrode without PU adhesive layer.
    • Fig. S15. SEM images of electrodeposited PEDOT:PSS on amine-functionalized Pt microwire electrode with PU adhesive layer.
    • Fig. S16. Strong adhesion of wet conducting polymer by PVA adhesive layer.
    • Fig. S17. Adhesion of thin spin-coated conducting polymers in wet physiological environment.
    • Legend for movie S1

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    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). Adhesion stability of wet PEDOT:PSS under cyclic bending deformations.

    Files in this Data Supplement:

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