From Microstructure to Mechanism: Joining-Form-Driven Optimization of Recovery Stress and Energy Harvesting in Nanofiber Membranes

Flexible multifunctional nanofiber membranes often consist of distinct functional components; however, the influence of interfiber microstructural integration on their coupled mechanical, thermal, and electrical performances remains poorly understood. Clarifying this structure-function relationship is essential for advancing high-performance nanofiber-based systems in wearable electronics and energy harvesting. This study systematically investigates how different nanofiber joining structures─specifically including independent alignment, side-by-side configuration, and coaxial core-shell arrangements─between shape-memory polyurethane (SMPU) and polyvinylidene fluoride (PVDF) nanofibers affect the composite membrane's actuation and sensing behavior. The coaxial configuration with an SMPU core and a PVDF shell exhibits the most effective synergy, achieving a shape-recovery rate of 98.72% and a recovery stress of 0.85 MPa, both significantly higher than those observed in the side-by-side and inverse core-shell arrangements. Under vibrational excitation at 40 Hz and 0.7 mm amplitude, the coaxial SMPU-core/PVDF-shell membrane delivers an output voltage of 98.54 mV─approximately a 170% increase over the nonintegrated parallel fiber design. Finite element simulations further confirm that the enhanced surface stress distribution under dynamic loading correlates with the observed improvements in mechanical and electrical outputs. Study establishes that rational microstructural coupling of functional nanofibers can significantly amplify device performance, offering a design paradigm for shape-conformal, self-powered sensing systems.