Design, Modeling, and Experiments of Electromagnetic Energy Harvester Embedded in Smart Watch and Wristband as Power Source

In this article, we investigated an embedded energy harvester to translate the kinetic energy of arm swing into electricity for powering smart watch and wristband. The embedded energy harvester integrates coaxially arranged motion capture unit, magnetic frequency-up converter, and electromagnetic transducer-based power generation unit to achieve high electricity production and power density. System model is built based on analytical and finite element method to estimate the performances and optimize the coils' parameters. To experimentally validate the performance of the embedded energy harvester, a highly compact prototype is fabricated and tested under pseudowalking excitation. The results show that the maximum power of 1.74 mW and power density of 346.61 μW/cm3at an excitation frequency of 0.65 Hz can be achieved by this device, which demonstrates great potential in realizing self-powered purpose for smart watch and wristband. Compared with the previous works, the proposed energy harvester accomplishes tremendous improvement both in power output and power density. To provide design guideline for various wearable devices, the constructed model is used to investigate the effects of inertial weight and speed transmission ratio on the power output and power density.