All-fiber acousto-electric energy harvester from magnesium salt-modulated PVDF nanofiber

Abstract

In this work, an all-fiber acoustoelectric nanogenerator (AAPNG) is fabricated by the hydrated metal salt (MgCl₂·6H₂O) (Mg-salt) reinforced polyvinylidene fluoride (PVDF–Mg) nanofibers as an active layer and interlocked conducting micro-fiber-based electrode for converting mechanical and acoustic energies into useful electrical power. It has been found that the electroactive phase content (∼84%) is enhanced in PVDF–Mg nanofibers due to the inter-molecular H-bonding moieties, the arrangement of the macromolecular chains of polyvinylidene fluoride (PVDF) in a layer-by-layer fashion, and the existence of an interfacial interaction between the Mg-salt and dimethylformamide (DMF) resonance structure and –CF₂ dipoles of PVDF. As a result, PVDF–Mg nanofibers possess superior piezoelectric charge coefficient (d₃₃ ≈ 33.6 pC N⁻¹) and figure of merit (FoM ≈ 12.7 × 10⁻¹² Pa⁻¹) with respect to neat PVDF nanofibers (d₃₃ ≈ 22 pC N⁻¹ and FoM ≈ 9.7 × 10⁻¹² Pa⁻¹). Benefitting from the ultrafast response time of ∼6 ms, AAPNG serves as an acoustoelectric sensor detecting low-frequency sound with an acoustic sensitivity (S_a) of 10 V Pa⁻¹, which is superior to that of neat PVDF nanofibers (S_a ∼ 266 mV Pa⁻¹). With the overall acoustoelectric energy conversion efficiency of ∼1.3%, AAPNG powers a range of commercial electronic gadgets, such as LEDs, capacitors, and LCDs. This makes it perfectly suitable for noise detection purposes as well as self-powered microphone applications. Additionally, AAPNGs can be realized as human motion monitoring systems, such as finger motion sensors that pave the way of futuristic robotic-based applications.