Performance enhancement of flexoelectric energy harvester by structural design

How to increase the output power and broaden its operating band is the key issue for the new flexoelectric energy harvester (FEH) to really move toward application. This study proposes a novel two-stage stepped variable-thickness cantilever beam FEH, differing from conventional uniform designs. Theoretical modeling, finite element analysis, and experimental validation are presented. The energy function is obtained by segmenting the flexoelectric cantilever beam according to the assumptions of Euler-Bernoulli beam and then discretized using the Galerkin method. Then, the Lagrange equations are employed to introduce the electromechanical coupling equations for the FEH. Steady-state response equations are obtained for harmonic excitation. Results demonstrate voltage and power density peak at resonance. Optimal matching impedance exists; power density near this impedance increases as flexoelectric layer thickness decreases, showing a significant size effect. Compared to uniform beams, the proposed FEH achieves a 71.8% reduction in first natural frequency and a 93.9-fold increase in power density. This work provides novel structural design strategies and theoretical guidance for high-performance FEHs.