Enhanced Dielectric and Thermal Properties of PVDF-AlN Films for Flexible Dual-Mode Sensors.

Poly(vinylidene fluoride) (PVDF), known for flexible wearable sensors and capacitive pressure sensing applications, stands out due to its premier piezoelectric property and excellent biocompatibility. However, the widespread deployment of PVDF-based devices is severely hindered by its inherent low dielectric constant, high dielectric loss, and poor thermal conductivity, which limit sensor sensitivity and response speed. In this paper, we propose a strategy to fabricate large-area high-performance AlN nanoflower-doped PVDF (APVDF) composite films, obtained with excellent dielectric properties (22 and 0.17 @ 1 Hz) and a low driving electric field of 40 MV/m. Especially, the bulk thermal conductivity reaches 14.97 W/(m·K), which is nearly 7% higher than that of commercial PVDF. Herein, the unique hierarchical nanoflower structure formed by selective oxidation of AlN may not only enhance the electroactive β + γ phase of PVDF but also constructs continuous thermal-conductive pathways to improve its heat-dissipation capability. Next, the APVDF-based dual-mode (pressure and electric field) sensor exhibits a fast piezoelectric response (20 ms) and high electric-field sensitivity (3.45 × 10-3 pF/(V/mm)) in a low-frequency range (1-10 Hz). This work paves the way for next-generation wearable electronics, human-machine interfaces, and tactile sensing systems, offering a solution to address the long-standing limitations of PVDF in advanced functional applications.