Niobium-Doped Bismuth Titanate-Loaded PVDF-HFP Flexible Composite Films for Self-Powered Stair Sensing and Emergency Alert Applications via Hybrid Mechanical Energy Harvesters

With the rise of demand for smart wearable and flexible electronic devices in the modern world, high-performance hybrid mechanical energy harvesters (HMEHs), which can easily convert biomechanical energy into electricity for powering a variety of portable electronic gadgets and operating smart sensors, have gained extensive interest. Herein, propose piezo/ferroelectric and dielectric niobium (Nb)-doped bismuth titanate (Bi₄Ti_3-xNb_xO₁₂, NBTO) plates, are proposed and synthesized by a molten-salt synthesis technique, and they are further embedded into the poly(vinylidene fluoride-co-hexafluoropropylene) (NBTO/PVDF-HFP) flexible composite film (CF) to construct a flexible HMEH. The prepared NBTO/PVDF-HFP CFs reveal good piezo/ferroelectricity, β-phase fraction, and dielectric properties, which can improve the electrical output performance of the HMEH. The 2 wt.% NBTO/PVDF-HFP CF-based HMEH exhibits high and stable electrical performance of ≈175 V, ≈5.8 µA, ≈76 µC m⁻², and ≈2.02 W m⁻², respectively. Furthermore, the durability and mechanical robustness analysis of the HMEH is conducted for several days. The real-time applications of the HMEH are demonstrated by harvesting the biomechanical energy obtained from daily human activities and powering various portable electronics. Also, the HMEH integrated with an Arduino microcontroller unit is employed as a smart sensor switch for implementing smart home/building stair-sensing applications and sending emergency e-mail alerts.