Structural Optimization and Output Characteristics of Ferrofluid‐Based Microtubular Electromagnetic Generator

Harvesting low‐ and ultralow‐frequency mechanical vibrational energy from the environment offers a promising solution for powering numerous sensor nodes within the internet of things. This study presents a ferrofluid‐based microtubular electromagnetic generator that efficiently captures ultralow‐frequency vibrational energy by leveraging the unique magnetization and fluidic characteristics of ferrofluid. The generator's output performance is systematically investigated with respect to key variables, including ferrofluid volume, magnetic field orientation, coil positioning, and the number of coil turns. The results show that optimal performance is achieved when the permanent magnets at both ends of the generator are arranged in a repulsive configuration, with the coils symmetrically distributed at both ends. The generator's output is also assessed under various low‐frequency vibration conditions across varying frequencies. Under an ultralow‐frequency seesaw swing vibration input (30° amplitude and 0.5 Hz frequency), the generator produced an open‐circuit voltage of 1.46 mV, a short‐circuit current of 62.5 μA, and a peak output power of 60.75 nW with a 20 Ω load. Remarkably, after 15 h and 27 000 continuous vibration cycles, the generator shows a minimal decline in output voltage, thereby demonstrating its reliability and long‐term potential for environmental energy harvesting applications.