Self-assembly of polyvinylidene fluoride (PVDF) and carbon nanotubes into flexible piezoelectric nanofiber transducers

We report a scalable fabrication strategy for flexible piezoelectric nanofiber transducers through a single-nozzle, self-assembling electrospinning process. Unlike traditional coaxial methods, this approach exploits the surface energy differential between polyvinylidene fluoride (PVDF) and multi-walled carbon nanotubes (MWCNTs) to drive the spontaneous formation of a core-shell architecture. The resulting 80 nm diameter fibers feature a predominantly crystalline β-phase PVDF shell, with molecular chains oriented along the [001] fibers axis, encapsulating a perfectly aligned MWCNT core that serves as an integrated internal electrode. Quantitative X-ray diffraction analysis confirms a five-fold increase in β-phase content relative to as-received PVDF powder, with a total crystallinity of 52% in the electrospun nanofibers. This unique coaxial configuration enables the demonstration of both direct and inverse piezoelectric effects in a single-step manufactured nanofiber device, without any post-fabrication electrical poling. The manufactured device yields an effective piezoelectric voltage coefficient of g_eff = 0.22 V.m.N⁻¹, comparable to values reported for fully poled bulk PVDF films, and an effective piezoelectric strain coefficient of d_eff = 2.8 pC.N⁻¹ under electrical excitation. The flexible, continuous nanofiber format, ten times thinner than spider silk, opens exciting possibilities for self-powered sensing, smart textiles, artificial skin, and structural health monitoring applications.