Electromagnetic energy harvester based on a finger trigger rotational gear module and an array of disc Halbach magnets

We propose a non-resonant finger-triggered electromagnetic energy harvester (EMEH) using multiple gear modules and an array of disc Halbach magnets, which can generate significant voltage and power under low input-frequency vibrations. The proposed EMEH converts the applied low frequencies into higher frequencies using a multiplying gear module and forwards the linear excitation to a rotational module by gear parts. The multiplying gear module was used for increasing the speed of magnet motion. In the energy generation part, an array of disc Halbach magnets were used for concentrating the magnetic flux toward the coils. The proposed energy harvester generated an open-circuit voltage of 1.39 V at an average power of 7.68 mW, with an optimal load of 36 Ω at an input frequency of 3 Hz. The prototype harvester offers a power density of 0.833 mWcm−3, which is much higher than those of recently reported EMEHs. We demonstrate wearable and portable electronics such as a stopwatch and pedometer-based on finger triggering. This study presents an important step toward low-frequency-vibration-powered devices for portable smart electronic applications and is expected to be widely applicable.