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Figure 3. Stretching and bending test on F-GNEC film sensor. (A) Schematic diagram of the principle of tensile and bending detection of F-GNEC film. (B) Comparison of ΔR/R₀ versus external tensile strains between the standard and pre-stretching films. (C) Specific ΔR/R₀ versus external tensile strains and gauge factor of pre-stretching F-GNEC film. (D) Comparison of ΔR/R₀ versus bending angles between the standard and pre-stretching film-based e-skin. (E) Multicycle bending of the pre-stretching F-GNEC film-based e-skin when bending at 30°, 60°, 90° and 120°. The inset depicts the response and recovery times under bending at 90°. (F) Multicycle bending of the pre-stretching F-GNEC film-based e-skin when bending at 90° with a frequency of 2, 1, 0.5 and 0.25Hz. (G) Stability and reliability test of pre-stretching F-GNEC film-based e-skin for 1000 bending 90° recovery cycles.