Self-powered smart watch and wristband enabled by embedded generator

Smart watches and wristbands are demonstrating great potential in industries such as health monitoring, sports training and entertainment. However, the limited battery life of these devices remains a key issue. We report an electromagnetic generator with coaxial topology that efficiently captures the motion of arm swing to produce electricity for smart watches and wristbands. This electromagnetic generator integrates a coaxially-installed motion capture mechanism, a magnetic frequency-up converter and a power generation unit in a highly compact and flat space, allowing it to be embedded in smart watches and wristbands. We use the finite element method to analyze the magnetic frequency-up conversion effect, generated voltage and transmission torque. We constructed a prototype to test the characteristics of the proposed embedded generator and its performance under simulated walking conditions. The average power generation and normalized power density were 1.74 mW and 820.38 μW/cm3·Hz2, which are, respectively, more than 4 and 10 times that of previous works. This embedded generator enables smart watches and wristbands to be self-powered.