Figure 2.

(a) Schematic illustration demonstrating the working mechanism of the sensor. Tunnel current occurs when the pressure is applied to the device; (b) output curves showing the difference in pressure sensitivity according to the sensor structure (reprinted with permission for Figure 2a,b from Ref. [25] Copyright 2014 American Chemical Society); (c) schematic illustration demonstrating the sensor fabrication method by using the liquid-driven transfer technique; (d) image of the skin-conformal sensor array; (e) gauge factor and maximum stretchability according to the number of transferred layer (reprinted with permission for Figure 2c–e from Ref. [39] Copyright 2017 John Wiley and Sons).