Science Advances

Supplementary Materials

This PDF file includes:

  • Section 1. Ferroelectric crystalline structures in PVDF/GO composites.
  • Section 2. Local temperature equilibrium model for the water droplet on e-skins.
  • Section 3. Characteristic time to reach thermal equilibrium for the water droplet on e-skins.
  • Fig. S1. Phase transition of the GO/PVDF composite films with various thermal treatments.
  • Fig. S2. FTIR spectra of the GO/PVDF composite films with GO loading concentrations of 0, 1, and 5 wt %.
  • Fig. S3. Crystalline structures of PVDF at different phases.
  • Fig. S4. Cross-sectional SEM images, crystallinity, and mechanical properties of the rGO/PVDF composite films with various rGO loading concentrations.
  • Fig. S5. Relative resistance (R/R0) variations of the e-skin (planar-structured rGO/PVDF composite film) after contact with the water droplet (temperature, 19.6°C).
  • Fig. S6. Relative resistance of e-skin as a function of the wide dynamic range of applied pressure from 10 to 49.5 kPa.
  • Fig. S7. Minimum pressure detection of ferroelectric e-skins.
  • Fig. S8. Stability of the piezoresistive pressure sensor under repetitive application and release of 25.5 kPa of pressure over 5000 cycles.
  • Fig. S9. Changes in the TCR and initial resistance values at different preloading weights.
  • Fig. S10. Effect of film conductivity on the piezoelectric outputs.
  • Fig. S11. Comparison of the piezoelectric and piezoresistive signal variations of e-skins in response to applied pressure with different frequencies (0.3 to 5.0 Hz).
  • Fig. S12. STFT spectrograms of the piezoelectric current signals for the high-frequency range (>80 Hz) obtained by scanning on PDMS films with periodic line patterns as a function of scanning speed.
  • Fig. S13. Effect of e-skin structure and fingerprint patterns for texture perception.
  • Fig. S14. Perception of hardness/softness of surface.
  • Fig. S15. Wearable e-skins for texture perception.
  • Fig. S16. Perception of fine textures for the low-frequency range (<30 Hz) obtained by scanning on PDMS films with periodic line patterns as a function of scanning speed.
  • Fig. S17. FTIR spectra for verifying residue solvent.
  • Fig. S18. Schematic illustrations of the double-casting and micromolding processes for the rGO/PVDF composite film with a microdome-patterned surface.
  • Fig. S19. Experimental setup for detection of dynamic pressure.

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