Wearable Piezoelectric Films Based on MWCNT-BaTiO₃/PVDF Composites for Energy Harvesting, Sensing, and Localization

Polymer-based lead-free piezoelectric composites provideenvironmentallyfriendly and scalable space for energy conversion and structural healthmonitoring. In this paper, multi-walled carbon nanotubes (MWCNT)-BaTiO3/polyvinylidene fluoride (PVDF) piezoelectric composite filmsfor energy harvesting, sensing, and localization were prepared. Thehighest & beta;-phase content of 90.21% in PVDF composite nanofiberswas achieved owing to the synergistic effect of MWCNT and BaTiO3 nanoparticles. The open-circuit voltage of the flexible piezoelectricnanogenerator based on interdigital electrodes reached 11.4 V at 2Hz and a bending strain of 4 mm with an optimal power and power densityof 8.67 & mu;W and 1.16 & mu;W/cm(2), respectively, andcan light up to 8 LED lights simultaneously. The output voltage didnot decay during 1800 cycles, which met the power and stability requirementsof a commercial capacitor. In addition, the prepared piezoelectricsensors exhibited anisotropy and high sensitivity. They had a maximumamplitude sensitivity of 93 dB, which was superior to the reportedPVDF-TrFE sensors and suitable for low-frequency signal monitoringin the range of 20-40 kHz. Localization accuracy was greaterthan 90% in linear and planar localization tests, demonstrating thepotential of preparing acoustic emission sensors. These propertiesfacilitate the reduction of the quantity of sensors required to identifythe source of damage.