Piezoelectric Vibration Energy Harvesting Using a Flexible Printed Circuit Board with a Built-in Hybrid Metamaterial/Solid-Core Structure

As the Internet of Things (IoT) ecosystem continues to expand, energy harvesting (EH) has become increasingly important for realizing self-powered sensor nodes. In this paper, we propose a vibration energy harvester based on a flexible printed circuit (VEH-FPC) that effectively utilizes the substrate area in IoT devices. To achieve both a lower resonance frequency and higher output power, an auxetic mechanical metamaterial (MM) with a negative Poisson’s ratio was incorporated into the elastic layer. In addition, to suppress the delamination of electronic components induced by the large deformation of the MM structure, a hybrid design was developed in which multiple electronic-component mounting regions were uniformly arranged over the cantilever and selectively implemented as a solid-core (SC) structure. Finite element method (FEM) analysis and experimental validation demonstrated that while preserving the electrical connectivity of the sensor, which is essential for proper FPC functioning, the hybrid design achieved a 20% reduction in resonance frequency and 1.8 times higher output power compared to the conventional SC design. Furthermore, the hybrid design prevented sensor delamination even under severe bending tests, demonstrating the coexistence of mechanical stability and enhanced power-generation performance.