Piezoelectric Effect Polyvinylidene Fluoride (PVDF): From Energy Harvester to Smart Skin and Electronic Textiles

Abstract

With the great demand for flexible self‐powered sensors and nanogenerators, polyvinylidene fluoride (PVDF) is widely investigated for outstanding piezoelectric and dielectric constant. In the pursuit for increasing β content, electrospinning is exhibited to be an effective method without external high voltage pooling or mechanical stretching and thus is considered a cost‐effective and simple method, because the molecular dipoles in the PVDF can be aligned during the process of electrospinning with high voltage field and stretching. The methods for improving piezoelectric characteristics are briefly introduced in this review, electrospinning fibers including uniaxial fibers, highly aligned fibers, core–shell fibers and Janus fibers are revealed, and research on theoretical modeling is carried out for efficiency in the design of piezoelectric nanogenerator. Last, studies on prospective applications based on electrospun PVDF and its copolymer PVDF‐TrFE, from sensors to smart skin, from energy harvesters to electronic textiles, are being conducted.

Electrospun Micro/Nanofiber-Based Biomechanical Sensors

“…In addition, PVDF-TrFE, a copolymer of PVDF, has emerged as a widely used piezoelectric sensing element due to its higher piezoelectric constant in comparison to pure PVDF polymers. 79,80 Figure 5A depicts the crystal structures of PVDF which consisted of three phases: α-phase, β-phase, and γ-phase. Generally, the αphase is the most common and the most thermodynamically stable, while the β-phase shows excellent piezoelectric response.…”

“…But PVDF exhibits superior flexibility, high chemical resistance, and remarkable thermal stability, which makes it become a preferred choice to develop nanofibrous membranes applied for the flexible piezoelectric sensor. In addition, PVDF-TrFE, a copolymer of PVDF, has emerged as a widely used piezoelectric sensing element due to its higher piezoelectric constant in comparison to pure PVDF polymers. , Figure A depicts the crystal structures of PVDF which consisted of three phases: α-phase, β-phase, and γ-phase. Generally, the α-phase is the most common and the most thermodynamically stable, while the β-phase shows excellent piezoelectric response.…”

Enhanced Piezoelectricity of PVDF-TrFE Nanofibers by Intercalating with Electrosprayed BaTiO3

“…Among these methods, electrospinning is a widely used method, capable of producing piezoelectric nanofibers with controllable diameters. The in situ poling and stretching result in high content of the polar crystalline β-phase without the need for post-processing. , However, as compared to ceramics, piezoelectric polymers mostly exhibit much lower piezoelectric coefficients, ,, which largely limits their application. Therefore, it is essential to increase their piezoelectricity.…”

“…1−6 Piezoelectric materials are of particular interest due to their capability of transducing mechanical stress to electrical signals and vice versa. Some examples of common piezoelectric materials include barium titanate (BaTiO 3 or BTO), 7,8 lead zirconate titanate 9,10 with a high piezoelectric coefficient, and flexible piezoelectric polymers, e.g., polyvinylidene fluoride (PVDF) 11,12 and its copolymers (e.g., poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE)). 13−15 Thanks to their high flexibility, high chemical resistance, and great biocompatibility, piezoelectric polymers are often used in developing wearable electronics.…”

“…Novel flexible polymer nanocomposites and microstructures have recently been widely utilized to develop flexible and stretchable sensors and energy harvesters. − Piezoelectric materials are of particular interest due to their capability of transducing mechanical stress to electrical signals and vice versa. Some examples of common piezoelectric materials include barium titanate (BaTiO 3 or BTO), , lead zirconate titanate , with a high piezoelectric coefficient, and flexible piezoelectric polymers, e.g., polyvinylidene fluoride (PVDF) , and its copolymers (e.g., poly­(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE)). − …”