Fig. 6: Piezoelectric harvesting properties of Single crystal wafer.

a Voltage and current outputs compared with measured PZT and P(VDF-TrFE) sample with similar dimension (5 * 5 * 2 mm) and applied stress. b Power density under various impedance loading of x = 0.25 crystal. c Comparison of piezoelectric energy harvester FOM among different piezoelectric materials. d Comparison of power density and material softness among different materials (see Supplementary Table 4 for references and details).