A tunable green power module for portable electronics and IoT sensors: design, fabrication, modeling, characterization, and implementation

•Eco-friendly power module for operating low-power IoT sensors.•Low-frequency specialization, i.e.,1–5 Hz.•Small handheld size of approximately 3.8 × 7.6 × 17.8 cm3.•Normalized power density of approximately 0.537 [mW/cm3 g2].•Generates 35 mW from hand-shaking at 3 Hz and 1.28 g m/s2 and 50 mW from jogging at 1.5 Hz and 1.7 g m/s2. [Display omitted] The unprecedented worldwide spread of portable electronics and low-power sensors in the era of Internet of Things (IoT) has amplified the demand for alternative sustainable and eco-friendly power sources. In this article, a novel tunable green power module for operating portable electronics is presented. The unique design of the power module allows for low-frequency specialization, i.e., less than 5 Hz, while maintaining a small handheld size, i.e., 3.8 × 7.6 × 17.8 cm3. A mathematical model is developed, and a prototype of the power module is fabricated. Both experiment and model are used to characterize the dynamic behavior of the power module. Results show good agreement between model simulations and experimental data. For a base-excitation of 0.15 g m/s2, the energy harvesting unit has a normalized power density of approximately 0.537 [mW/cm3. g2]. In this article, the ability of the power module to light a group of LEDs and charge a smartphone from human body motion is demonstrated. In these real-world demonstrations, the power module was able to generate 35 mW from hand-shaking at 3 Hz and 1.28 g m/s2 and 50 mW from jogging at 1.5 Hz and 1.7 g m/s2. Compared to state-of-the-art, the presented power module displays unique features, including its ability to harvest low-density vibrations that are characterized by low frequencies and accelerations.