Self-Poling Polyvinylidene Fluoride-Based Piezoelectric Energy Harvester Featuring Highly Oriented β-Phase Structured at Multiple Scales

Abstract

Self-poling poly­(vinylidene fluoride) (PVDF) featuring uniformly aligned dipoles can convert mechanical vibrations into electrical energy without post-poling treatment, which is a topic of intense interest in self-powered flexible electronics. However, the current strategies to align PVDF rich in β-crystals have some limitations, such as complex processing, low productivity, and so on. Herein, a self-poling flexible PVDF generator structured with a highly oriented β-phase was prepared via a normal melt processing pathway, by combining flow-induced crystallization with the stabilizing effect of dopamine-functionalized carbon nanotubes (P-CNTs) on the oriented molecules. In this case, the intense flow field exerted by microinjection facilitated the gauche–trans transition and uniform orientation, while with the help of strong interaction between O–H groups of P-CNTs and F–C groups of PVDF, P-CNTs recruited and immobilized the neighboring short chains onto the surface, suppressing the molecular relaxation. As a result, rich electroactive β-phases with preferential alignment characteristics were cultivated in situ, resulting in intrinsic self-oriented dipoles. The extraordinary piezoelectric properties of the PVDF were fully utilized even without polarization treatment, and the open-circuit voltage density reached ∼11 V/cm2, with over 4-fold improvement as compared to that of the randomly oriented sample fabricated by conventional cast method. Finally, the potential application as a robust energy harvester was explored by converting irregular mechanical energy from finger movements into utilizable electric energy, lighting green light-emitting diodes. This multi-scale control from crystalline composition to morphology based on flow-induced crystallization is achieved by simple melt-processing and thus can be suitable for large-scale continuous fabrication of self-poling piezoelectric PVDF energy harvesting devices.

Current Advances and Future Perspectives of Advanced Polymer Processing for Bone and Tissue Engineering: Morphological Control and Applications

“…Special crystal modification such as the β crystal of PVDF can also be scalarly fabricated with the assistance of the ultrahigh shear in micro-injection. Nie ( Guo et al, 2020 ) successfully prepared PVDF piezoelectric parts with a relative fraction of β crystals of 52% by micro-injection, and the open-circuit voltage density reached ∼11 V/cm 2 , with over 4-fold improvement as compared to that fabricated by conventional cast method. Except from crystal, the ultrahigh shear can also promote the mechanism of in-situ fibrillation.…”

Surface silanized MWCNTs doped PVDF nanocomposite with self-organized dipoles: an intrinsic study on the dielectric, piezoelectric, ferroelectric, and energy harvesting phenomenology

“…14 The enhancement in b-fraction arises from the interaction between the polymer and the surface charge. 15 Guo et al 16 modied CNTs with dopamine, which uniformly organized the dipoles in the PVDF nanocomposite. Similarly, Mandal et al 17 modied the surface of MWCNTs with 3-aminoethyl imidazolium bromide, which assisted in the good distribution of MWCNTs in the PVDF matrix.…”

Polyvinylidene Fluoride Energy Harvester with Boosting Piezoelectric Performance through 3D Printed Biomimetic Bone Structures

“…Piezoelectric materials are of great significance in practical applications as they can convert compressive/tension stresses into electric charge or vice versa . Over the past few years, piezoelectric polymer devices have been widely used in sensors, , actuators, , energy harvesters, − and other fields − due to their high energy conversion efficiency and high piezoelectric sensitivity. , The traditional piezoelectric polymer devices are mostly made of a thin-film structure, which cannot make full use of the normal space to produce sufficient strain, leading to limited piezoelectric output. − To improve the piezoelectric output of the device, structures such as micropores, , micropillars, , micropatterns, , and microfibers − were introduced into the polymer film, which can cause a stress concentration effect and greatly magnify the strain as well as the piezoelectric output. , …”