Nanofiber-based wearable energy harvesters in different body motions

Abstract In this study, flexible energy harvesters based on lead zirconate titanate (PZT)/shape memory polyurethane (SMPU) nanofibers were prepared and made wearable for energy harvesting from human body movements while ensuring flexibility. The results obtained showed that there is a relationship between the piezoelectric and energy harvesting properties of the proposed PZT/SMPU energy harvesters, and the alignment degrees and motion modes. The 0°-aligned energy harvester—wherein nanofibers are parallel to the longitudinal direction—showed higher piezoelectric properties and induced higher output voltages because of the bending motion compared to nanofibers aligned randomly-, at 90°-, and at 45°-. Practical tests showed that flexible energy harvesters can efficiently convert mechanical energy into electricity when subject to different body motions such as bending, twisting, and applied pressure. The maximum output voltages generated by energy harvesters with 0°- and 45°-aligned nanofibers were 537 and 55 mV when they were subjected to finger bending and wrist twisting motions, respectively; this represents an increase of at least 28% compared to that of other samples. Therefore, these findings provide insights and strategies related to the optimal arrangement of nanofibers in wearable energy harvesters and improvement in their energy harvesting efficiency with respect to different body part motions.