Investigation of the Different WO₃ Nanofiller Morphology Influence on the Piezoelectric Properties of WO₃-PVDF Nanocomposites for Self-Powered Biomedical Devices and Flexible Wearable Sensors

Lead-free piezoelectric polymer nanocomposite materials are emerging as promising materials for biomedical energy applications and flexible, wearable electronics due to their tailorable and biocompatible properties. However, optimizing their piezoelectric performance through effective nanofiller integration remains a challenge. While previous studies have explored various nanomaterials in poly(vinylidene fluoride) (PVDF) to enhance its β-phase content, the influence of nanofiller morphology, surface charge, and crystal structure on piezoelectric properties is not well understood. Moreover, the long-term stability and practical applicability of such materials require further investigation. This study addresses these gaps by developing a self-polarized energy harvester and biomechanical pressure sensors using PVDF as the matrix and tungsten trioxide (WO3) in various morphologies as nanofillers. In order to develop an experimental understanding of the interactions between polymers and nanomaterials, the same nanofiller with varying morphologies, crystal structures, and surface charges is used. Out of the four distinct morphologies, the nanoflowers with the highest surface charge and monoclinic crystal structure, which had a zeta potential of −58.4 mV, performed best with the PVDF matrix in terms of producing β-phase content. A systematic approach was adopted to optimize the β-phase content of PVDF and determine the ideal nanofiller concentration for enhanced energy generation by fabricating energy-generating devices. A prototype was fabricated with the optimized combination of a polymer nanocomposite encapsulated in flexible polydimethylsiloxane (PDMS) packaging. The fabricated prototype demonstrated an output voltage of 107 V under biomechanical force ranging from 10 to 11 N, achieving a maximum power density of 377.46 μW/cm2 at 1 MΩ resistance. The real-time applications of the prototype are demonstrated as a gas leakage detection system and a wireless patient monitoring system with a cell-phone-based interface as a display.