Solvent Casting Reprocessing of Poly(vinylidene fluoride-co-hexafluoropropylene)-Based Nanocomposite Sensors: An In-Depth Study on Recyclability and Performance

Wearable electronics have gained increasing attention due to their potential in real-time health monitoring applications. However, the environmental impact and waste associated with non-recyclable materials used in these devices remain critical challenges. This study investigates the reprocessing and recyclability of flexible strain sensors based on Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanocomposites reinforced with carbon nanotubes (CNT) and graphene nanoplatelets (GNP). The nanocomposites are subjected to multiple recycling cycles using a solvent casting method, and their electrical and electromechanical properties are thoroughly analyzed. Microstructural characterization revealed improved nanoparticle dispersion with recycling, albeit with distinct behavior for CNT and GNP due to differences in aspect ratio and geometry. Electrical tests demonstrated a reduction in conductivity for CNT-based sensors due to nanoparticle breakage, while GNP-based sensors exhibited stable conductivity. Electromechanical tests indicated enhanced sensitivity after recycling, with GNP-based sensors showing superior robustness. Proof-of-concept tests, including monitoring knee joint movements and breathing patterns, validated the functionality of recycled sensors in health monitoring applications. The findings highlight the potential of reprocessed PVDF-HFP nanocomposite sensors as sustainable, high-performance materials for wearable electronics.