A human locomotion inspired hybrid nanogenerator for wrist-wearable electronic device and sensor applications

Abstract

The availability of realistic, wearable efficient energy harvesters for powering body-worn IoT devices and health monitoring sensors is essential, in order to reduce the dependence of these wearable electronic devices, on batteries. Herein, we demonstrate a novel curve-shaped wearable hybridized electromagnetic-triboelectric nanogenerator (WHEM-TENG), operating as a fully-enclosed light-weight low-frequency energy harvester, driven by human motion. The WHEM-TENG incorporates the swinging behavior of a human arm during locomotion, and the freestanding rolling mode of a magnetic ball. Simulations of the magnetic flux density and the triboelectric surface potential assisted in improving the design and performance of the nanogenerator. The harvester device was manufactured using a 3D-printing method, which makes the fabrication process faster, easier, and more cost-effective than traditional methods. The 3D-printing material was used as triboelectric material for the nanogenerator. Experiments illustrate that at the low input frequencies characteristic of walking and running, the electromagnetic generator (EMG) and triboelectric nanogenerator (TENG) deliver peak power densities of 5.14 mW/cm3 and 0.22 µW/cm3, across load resistances of 49.2 Ω and 13.9 MΩ, respectively. Moreover, we also demonstrate that the WHEM-TENG can drive a commercially available electric wrist-watch continuously for 410 s from the power generated by just 5 s of running activity. Also, we demonstrate a self-powered heart-rate sensor driven by the nanogenerator. The electrical output of this distinctively structured device is promising for optimization of similar hybrid wearable energy harvesters, and for practical applications, towards the development of self-powered wearable smart bands/watches and fitness/health monitoring sensors.