Exfoliated Graphene Nanoplatelets and Expanded Graphite-Incorporated Poly(vinylidene fluoride) Nanocomposites for Piezoelectric Nanogenerators and Real-Time Motion Detection

The growing demand for intelligent, autonomous, and interconnected environments drives the need for self-powered sensors capable of real-time monitoring and smart control. Here, we report a flexible piezoelectric nanogenerator (PENG) based on monolithium adipate (Li-AA) exfoliated graphene nanoplatelet (GNP) and expanded graphite (EG)-incorporated poly(vinylidene fluoride) (PVDF) nanocomposites for smart gatekeeping application. The Li-AA-assisted exfoliation strategy significantly enhances nanofiller dispersion and interfacial interactions within the PVDF matrix, promoting a higher electroactive β/γ-phase content of ∼91.4%, compared to ∼71% in pristine PVDF. The optimized PVDF/GNP:Li-AA (1:6) nanocomposite-based PENG delivers an impressive output voltage of ∼64 V and a power density of ∼49.23 μW/cm2, outperforming expanded graphite-based PENG (∼60 V, ∼45.21 μW/cm2), and retains stable performance over 10,000 cycles. The device, coupled with IoT, functions as a self-powered smart gatekeeping sensor, accurately distinguishing entry and exit motions without external energy input. This work establishes a scalable pathway for next-generation PVDF-based nanocomposites that enable intelligent, energy-autonomous infrastructure and advance the practical realization of sustainable smart security systems.