An all-in-one energy harvester module comprising a top piezoelectric layer, a bottom piezoelectric layer, and a middle triboelectric layer was fabricated based on flexible piezoceramic nanofibers to serve as a power source for wearable devices. The top and bottom piezoelectric layers were manufactured by modularizing electrospun piezoceramic nanofibers with an interdigitated electrode, and the energy harvesting characteristics were maximized by laminating the single modules in z-axis array arrangements. The triboelectric layer was manufactured by attaching polydimethylsiloxane on both sides of an electrode layer, and the energy harvesting characteristics were controlled according to the surface roughness of the triboelectric modules. The output voltages of the individual energy harvester modules of the all-in-one module were individually or integrally measured by hand pressing the lower and upper parts of the module. The all-in-one energy harvester module generated a maximum voltage (power) of 253 V (3.8 mW), and the time required to charge a 0.1 μF capacitor to 25 V was 40 s. The results of a simulated energy harvesting experiment conducted on the all-in-one energy harvester module showed that 42 LED bulbs arranged in the shape of the "KICET" logo could be turned on in real time without charging, and a mini fan consuming a power of 3.5 W was operated after charging a 10 μF capacitor for 250 s. This work shows the potential of the all-in-one module as an ecofriendly flexible energy harvester for operating wearable devices.
Keywords: energy harvesting; flexible all-in-one module; nanofibers; piezoelectric; triboelectric.