Piezo-Phototronic PVDF/HfO₂/Nano-Cu Heterostructured Thin Film for Flexible Self-Powered Multimodal Sensing

The pursuit of multifunctional sensors has intensified due to their potential for integrated, efficient operation. However, realizing a flexible material that combines simplicity in the fabrication process with high performance and multifunctionality remains a formidable challenge. In this study, a multi-interface heterostructured nanofiber membrane composed of Polyvinylidene fluoride (PVDF), HfO₂, and nano-copper is fabricated, leveraging the synergistic interplay of piezoelectric and piezo-phototronic effects for flexible, self-powered sensing. The incorporation of hafnium oxide (HfO₂) and nano-Cu enhances the crystallinity of the piezoelectric β-phase and improves the dielectric properties, substantially boosting electromechanical performance. The resultant piezoelectric sensor achieves an output voltage of 15V and maintains stability over 5000 cycles at 5 Hz, enabling precise detection of human motions. Meanwhile, the PVDF/HfO₂-based photodetector exhibits broadband sensitivity (from near-UV to near-IR), high photoresponsivity (5.67 mA W^-1), high detectivity (4.14×10¹¹ Jones), and rapid response (600 µs rising, 53 µs falling). Critically, the device demonstrates a 28.6% current enhancement under simultaneous light and pressure, highlighting a strong piezo-phototronic effect. This work presents a multifunctional fiber film for dual-mode sensing (pressure & light), with promising applications in wearable electronics and aerospace systems. Its straightforward fabrication and high performance offer a viable pathway toward next-generation, flexible, self-powered sensors.