Piezoelectric energy harvester with tip 3D-printed bi-stable asymmetric raceway for effective harvesting of ultralow-frequency and low-level vibration energy

Bi-stable piezoelectric vibration energy harvester (B-PVEH) with magnetic interaction has attracted immense attention due to its wide bandwidth and high efficiency. However, its dynamic performances severely affected by the position distribution and distance of the magnets, which greatly limits the effective harvesting of ultralow-frequency and low-level vibration energy. To overcome this issue, a novel B-PVEH with a tip 3D-printed bi-stable asymmetric raceway is proposed. It consists of a piezoelectric cantilever beam, a tip 3D-printed bi-stable asymmetric raceway (BAR) and a linear bearing-spring mechanism (L-BSM). By appropriately self-defining design the two stable equilibrium points to form continuous convex and concave contour surfaces of the BAR, a time-varying and tunable nonlinear force will be generated by the interaction between the 3D-printed BAR and the L-BSM, which causes an asymmetric bi-stability of the BPVEH, resulting in high dynamic generations. The self-defining design philosophy and flowing chart of the 3D-printed BAR was firstly investigated, and then the nonlinear electromechanical coupling dynamic model of the B-PVEH was established to theoretically and experimentally testify the design philosophy. The research results indicate that the proposed B-PVEH with three different 3D-printed BARs has bandwidth of inter-well motion of 4.6 Hz (1.6 Hz-6.2 Hz), 2.6 Hz (3.1 Hz-5.7 Hz) and 1.7 Hz (3.9 Hz-5.6 Hz) respectively, which meet the requirement of ultralowfrequency vibration energy harvesting. They also achieve high normalized power density (NPD) of 16.163, 15.6 and 14.151 (mW.cm- 3.g- 2.Hz- 1) respectively under low-level excitation of 2 m/ s2. The lab and field applications demonstrate that the fabricated prototypes meet the power supplying requirements of low-powered electronic devices.