Strontium-Modified BaTiO₃ Composite Nanogenerators for Flexible and Self-Powered Human-Machine Interactions

Flexible piezoelectric nanogenerators (PENGs) have emerged as promising energy-harvesting devices for wearable electronics and self-powered human-machine interfaces. In this study, barium strontium titanate (BSRT) with varying Sr-substitution ratios was synthesized via a conventional solid-state reaction route, and its structural and functional properties were systematically evaluated. X-ray diffraction analysis confirmed the formation of phase-pure tetragonal perovskite BSRT and successful incorporation of Sr into the BaTiO₃ lattice. The composition with 5% Sr exhibited optimized structural characteristics and was selected for device fabrication. Flexible BSRT-polydimethylsiloxane (PDMS) composite films were prepared and employed as the active layer in a sandwich-structured PENG. The electrical output performance was tuned by varying the filler loading, with an optimal composition of 15 wt % yielding a peak-to-peak voltage of 60 V and a short-circuit current of 5 μA under periodic mechanical excitation. The device further demonstrated stable capacitor charging behavior, excellent mechanical durability, and the capability to power multiple light-emitting diodes. Additionally, a self-powered human-machine interface was demonstrated by integrating multiple PENG units with a microcontroller, enabling real-time slide navigation through simple finger tapping motions. This work highlights the potential of BSRT-based flexible PENGs as efficient energy harvesters and self-powered sensing platforms for next-generation wearable and interactive electronic systems.