Fig. 8.

Stretchable resistive (a–f) and capacitive (g–k) strain gauges using CNT networks. a Schematics of the fabrication process and working mechanism of the resistive strain gauge. b In situ SEM image of the SWCNT array under a 100 % strain, showing the transverse fracture of the film. c Relative change in resistance for up to 10,000 stretching cycles with strains of 100, 150, and 200 %. d–f A strain gauge attached to a bandage and adhered to the throat (d) used to detect human breathing (e) and phonation (f). Reproduced from ref. [29]. g Operating mechanism of capacitive strain gauge using SWCNT film as stretchable electrodes. h Relative changes in resistance of the SWCNT/PDMS composite electrodes under progressively increasing strains. i Relative changes in capacitance under stretch-release cycles with progressively increasing strains. j Relative changes in capacitance after repeated stretch-release cycles with maximum strain of 100, 150, and 200 %. k Demonstration of using the capacitive strain gauge to monitor the motion of human fingers. Top panel: photographs of a strain gauge attached to the finger with different gestures. Bottom panel: The capacitive response at each corresponding stage. Reproduced from ref. [84]