A Novel Micro-Electromagnetic Harvester with Geometry-Based Optimization for Efficient Low-Frequency Energy Harvesting

This study introduces a micro-electromagnetic energy harvester designed for low-frequency vibrations below 11 Hz, suitable for low-power applications such as wearable electronics, human motion sensing, and structural monitoring. The harvester operates by inducing current in a stationary copper coil through the oscillatory motion of a magnet along the z-axis. Three coil geometries—circular, pentagonal, and square—were modeled using COMSOL Multiphysics to evaluate the influence of shape and coil turns on performance under identical vibrational conditions. Simulation results showed that the square coil with 10 turns achieved the highest efficiency, producing up to 800 mV and 2.8 mW at 10 Hz. A prototype based on the circular coil design was fabricated using standard lithography on an FR4 substrate and experimentally tested. The fabricated harvester generated an open-circuit voltage of up to 300 mV and a maximum output power of 1.75 mW under matched-load conditions. The experimental results closely matched simulation data, confirming the reliability of the design. Magnetic flux linkage analysis revealed that square geometries enhance electromagnetic coupling due to localized edge field intensification. The vibration excitation setup, including a shaker system, laser vibrometer, and Gaussmeter, ensured controlled testing and reproducibility. This work demonstrates the importance of coil geometry in optimizing energy harvesting performance and offers a viable solution for low-frequency energy conversion in micro-scale systems.