Fig. 3 Please replace figure 3 with attachment file.

a Response vs strain curves of S-50/60/70/80 sensors. b I–V curves of the S-50 sensors under strains from 0 to 0.39%. c Dynamic response curves of S-50 sensor under various applied strains. d Dynamic response curve under a stair-like strain change. e Fast response and recovery speed of S-50 sensor. f Relative resistance variations under cyclic loading–unloading with a strain of 0.19% at the frequency of 0.25 to 2 Hz. g Current–time curves of the S-50 sensor for 5000 loading/unloading cycles with an applied strain of 0.25%. h Schematic diagram of the strain sensing mechanism