Fig. 3: APE pyramid sensor unit.
a, Simulated deformation and stress distribution in the longitudinal section of a pyramid sensor unit under vertical pressure. b,c, Curves showing the relative change in conductance (ΔG/G0) versus pressure for the APE sensor unit in the 0–30 kPa (b) and 0–500 kPa (c) pressure ranges. d, Simulated deformation and stress distribution in the longitudinal section of a sensing unit under an oblique force. a,b, constant coefficients related to sensor geometry and electrode positions; R1,R2, resistance measured at the electrodes on the bottom of the sensor unit. e,f, Simulated pressure distribution at the bottom of the APE sensor unit under normal force (e) and shear force (f). g,h, Curves showing the relative change in potential (ΔU/U0) versus pressure, as measured by 4 electrodes (U1–U4) on the bottom of the APE sensor unit in the 0–1.3 kPa (g) and 0–55 kPa (h) pressure ranges. The inset in g shows a schematic of the sensor unit; the inset in h shows an expansion of the data outlined by the red box. Vcc, voltage at the common collector. i, Profile showing how the potential measured by the first electrode (U1) on the bottom of the sensor unit changes with time over 12,000 cycles of 0–1.6 kPa loading. Insets: the curves for the first 20 cycles (left) and for cycles 10,001–10,020 (right).
