Abstract
This article presents a novel, low-frequency, tunable, and wearable power module that can power portable electronic devices by harvesting power from human body motion. The device features a unique spring system that allows the power module to harvest at low-frequency range; ideal for integrating into daily human activities. The unique design of the power module allows for low-frequency specialization, i.e., less than 5 Hz. The spring system can be tuned into one of two modes. The optimum load resistance is determined to be 96 Ω. When shaken by hand and connected to a smartphone, the power module outputs a power of approximately 35 mW. The power module is handheld and has a small volume of roughly 3.8 × 7.6 × 17.8 cm3. An internal power management circuitry that can convert the AC output voltage from the harvester into a DC voltage is built and tested experimentally. In this work, the ability of the power module to utilize vibrations from human body motion in charging a smartphone is demonstrated.