Fig. 2: Schematics and simulation results of the IENG.

a Basic structure of the three-dimensional intercalation electrode. Each part of piezoelectric material is sandwiched by a pair of well-matched electrodes. The adjacent parts of piezoelectric material are polarized with opposite direction, and all the parts connected in parallel forming a three-dimensional device. The red and blue arrows represent the projection of electric dipole moment along the thickness direction. When driven by an external force, each unit in the IENG simultaneously generates small current in the same direction, then adding up to be a large output current through the three-dimensional intercalation electrode. b Distribution of piezoelectric potential in different units when the same piezoelectric layer model is divided into 1, 2, 3, 4, 6 and 12 units by different pairs of intercalation electrode. c The corresponding output charge density in short-circuit condition and output voltage in open-circuit condition generated by different units.