Enhanced piezoelectric performance of PVDF/MWCNTs energy harvester through a 3D-printed multimodal auxetic structure for smart security systems

Abstract

Piezoelectric energy harvesters (PEHs) have attracted considerable attention over recent decades for their ability to convert mechanical energy into electrical energy. However, the current landscape is characterized by a lack of structural variety, which constrains the potential for notable performance improvements and the expansion of applications of these devices. To address these challenges, three distinct metamaterial structures are investigated through numerical simulations in this study. An auxetic, reentrant shape with carefully optimized dimensions was found as the best choice for the development of an efficient Polyvinylidene fluoride/multi-walled carbon nanotubes (PVDF/MWCNTs) PEH with optimized composition. This structure exhibits a remarkable capability to activate three different piezoelectric modes. Given it is polarization in the z-direction, the structure activates both d31 and d32 modes upon stretching in the x-direction, benefitting from the structure's negative Poisson's ratio and generating an open circuit voltage of 14.8 V. In contrast, compression in the z-direction activates the d33 mode, resulting in an open-circuit voltage of 28.2 V. This design allows the harvester to charge a 1 μF capacitor to 22 V within 260 s. The structure's feasibility is further evidenced by its fabrication using Fused Deposition Modeling (FDM) 3D printing technology. To further extend its practicality and real-world application, the PEH can be seamlessly integrated into large-scale commercial, industrial, and residential flooring, offering a novel approach to security systems. In this innovative approach, the PVDF/MWCNTs PEH converts the compressive force of footsteps into electrical signals. These signals serve as triggers for an integrated alarm system. Essentially, the electrical signal functions as a switch: its transmission acts like a closed switch that triggers the activation of the alarm system. Conversely, the absence of the signal is an open switch, indicating that no external force is acting on the tiles and a safe condition is maintained. Remarkably, the PEH can produce a voltage of 19.8 V when activated by the footsteps of a 60 kg person, demonstrating its practical utility.© 2017 Elsevier Inc. All rights reserved.